Extension:Scribunto/Lua reference manual/it

Questo manuale documenta nei suoi utilizzi in MediaWiki con l'estensione. Alcune parti derivano dal manuale di riferimento al Lua 5.1, disponibile sotto licenza MIT.

Introduzione


Per iniziare
In una wiki di MediaWiki con Scribunto abilitato, creare una pagina con un titolo iniziante per "Modulo:", per esempio "Module:Bananas". All'interno di questa nuova pagina, copiare il seguente testo:

Salvalo, poi in un'altra pagina (che non sia un modulo) scrivi:

Escluso il fatto che si deve sostituire "Banane" con qualunque nome sia stato scelto per il modulo, l'istruzione  verrà sostituita con il testo ritornato dalla funzione, che in questo caso sarà "Hello, world!"

Generalmente è una buona idea invocare il codice Lua dal contesto di un template. Questo significa che, dal punto di vista di una pagina chiamante, la sintassi è indipendente dalla logica del template, che sia implementato in Lua o in wikitesto. It also avoids the introduction of additional complex syntax into the content namespace of a wiki.



Struttura del modulo
Il modulo stesso deve ritornare una tabella Lua contenente le funzioni che possono essere chiamate con. Generalmente, come mostrato sopra, una variabile locale è dichiarata contenente una tabella, le funzioni sono aggiunte in questa tabella e la tabella è ritornata alla fine del codice del modulo.

Ogni funzione non aggiunta in questa tabella, sia globale che locale, non sarà accessibile via, ma le globali potrebbero essere accessibili da altri moduli caricati utilizzando. In un modulo è generalmente una buona pratica dichiarare come locali tutte le funzioni e le variabili.



Accedere ai parametri dal wikitesto
Le funzioni richiamate da  riceveranno un singolo parametro, l'oggetto frame. Per accedere ai parametri passati da, il codice di solito userà la  |tabella   dell'oggetto frame; è anche possibile accedere ai parametri passati dal template contenente   utilizzando   e accedendo agli   di tale frame.

L'oggetto frame è anche utilizzato per accedere a funzionalità specifiche relative al parser del wikitesto, come richiamare funzioni parser, espandere template ed espandere stringhe arbitrarie di wikitesto.



Ritorno del testo
La funzione del modulo dovrebbe di solito ritornare una singola stringa; qualsiasi siano i valori ritornati, passeranno attraverso tostring ed in seguito saranno concatenati senza alcun separatore. Questa stringa sarà incorporata nel wikitesto come risultato di.

A questo punto della pagina, i template sono già stati espansi, le funzioni parser ed i tag sono già stati processati e le trasformazioni presalvate (ad esempio l'espansione tilde e pipe trick) sono già state eseguite. Pertanto il modulo non può utilizzare queste funzionalità nel suo testo di output. Per esempio, se un modulo restituisce, la pagina leggerà "Ciao, mondo!  ".

D'altro lato, subst è gestito in una fase precedente dell'elaborazione, così con  solo altri tentativi di sostituzione saranno elaborati. Poiché la fallita sostituzione rimarrà nel wikitesto, essi verranno elaborati nella modifica successiva. Questo generalmente dovrà essere evitato.



Documentazione del modulo
Scribunto consente di documentare i moduli associando automaticamente il modulo a una pagina di documentazione; per impostazione predefinita, la sottopagina "/doc" del modulo viene utilizzata per questo scopo ed è inclusa al di sopra del codice sorgente sulla pagina del modulo. Ad esempio, la documentazione di "Modulo:Banane" si trova in "Modulo:Banane/doc".

Questo può essere configurato usando i seguenti messaggi di sistema

specificate qui saranno interpretate come wikitesto piuttosto che come codice sorgente Lua e possono non essere utilizzate con. L'impostazione predefinita "Module:$1/doc", ovvero la sottopagina /doc del modulo. Notare che le funzioni parser ed altre espansioni in parentesi possono non essere usate in questo messaggio.
 * —Imposta il nome della pagina utilizzata per la documentazione. Il nome del modulo (senza il prefisso Module:) passa come . Se nel titolo del modulo, le pagine
 * — Messaggio mostrato quando la pagina di documentazione non esiste. The name of the page is passed as . The default is empty.
 * — Message displayed when the doc page does exist. The name of the page is passed as . The default is to transclude the documentation page.
 * — Header displayed when viewing the documentation page itself. The name of the module (with Module: prefix) being documented is passed as . The default simply displays a short explanation in italics.

Notare che i moduli non possono essere categorizzati direttamente e non possono avere collegamenti interwiki aggiunti direttamente, a meno di inserirli nei commenti (vedi sotto). Questi possono essere posti nella pagina di documentazione tra i tag , attraverso cui saranno applicati al modulo quando la pagina di documentazione sarà inclusa nella pagina del modulo.



Token
I nomi (detti anche identificatori) in Lua possono essere qualsiasi stringa di lettere, cifre, e caratteri di sottolineatura, purché non inizianti con una cifra. È presente la distinzione della capitalizzazione nei nomi; "spa", "Spa", ed "SPA" sono nomi differenti.

Le seguenti parole sono riservate e non possono essere utilizzate come nomi:



I nomi che iniziano con un  + lettera maiuscola sono riservati alle variabili globali interne di Lua.

Altri token sono:


 * - negation, subtraction
 * - code comments
 * - negation, subtraction
 * - code comments
 * - negation, subtraction
 * - code comments
 * - negation, subtraction
 * - code comments
 * - code comments

Commenti
Un commento inizia con  ovunque al di fuori di una stringa. Se  è subito prima una parentesi quadra aperta, il commento continua fino alla corrispondente parentesi quadra di chiusura; altrimenti il commento prosegue fino al termine della riga.



Tipologie di dati
Lua è un linguaggio dinamico, il che significa che le variabili e gli argomenti delle funzioni non hanno tipo, solo i valori assegnati hanno un tipo. Tutti i valori hanno un tipo.

Lua ha otto tipi base di dati, tuttavia solo sei sono pertinenti all'estensione di Scribunto. La funzione  darà il tipo di un valore.

La funzione  convertirà un valore in una stringa. La funzione  convertirà un valore in un numero, se possibile, altrimenti restituirà. Non ci sono funzioni esplicite per convertire un valore in altri tipi di dati.

I numeri sono convertiti automaticamente in stringhe se sono usati dove è prevista una stringa, per esempio dove è usato un operatore di concatenazione. Le stringhe riconosciute da  sono automaticamente convertite in numeri de usate con operatori aritmetici. Quando un valore buleano è previsto, tutti i valori diversi da  e   sono considerati essere veri.

nil
"nil" è un tipo di dato, che esiste per rappresentare l'assenza di un valore.

"nil" può non essere usato come chiave in una tabella, e non c'è differenza tra una chiave di tabella non assegnata ed una chiave con assegnato il valore "nil".

Quando convertito in una stringa, il risultato è "nil". Quando convertito in un buleano, "nil" vale come falso.

boolean
Valori buleani sono  e.

Quando convertiti in testo, il risultato è "vero" o "falso".

Diversamente da quanto avviene in molti altri linguaggi di programmazione, i valori buleani possono non essere convertiti direttamente in numeri. Inoltre, sempre a differenza di quanto avviene in molti altri linguaggi di programmazione, solo false e nil sono considerati falsi per la conversione buleana; il numero 0 e la stringa vuota sono entrambi considerati veri.

stringhe
Le stringhe Lua sono considerate serie da 8 bit; spetta all'applicazione interpretarli con una particolare codifica.

Le stringhe letterali possono essere delimitate da virgolette singole o doppie ; come in JavaScript e diversamente da PHP, non c'è differenza tra i due. Le seguenti sequenze alternative sono riconosciute:


 * (campana/bip, byte 7)
 * (backspace, byte 8)
 * (tabulazione orizzontale, byte 9)
 * (nuova riga, byte 10)
 * (tabulazione verticale, byte 11)
 * (form feed, byte 12)
 * (ritorno a capo, byte 13)
 * (virgolette doppie, byte 34)
 * (virgolette semplici, byte 39)
 * (barra obliqua "\", byte 92)

Una nuova riga letterale può essere inclusa anche in una stringa dopo una barra obliqua. I byte possono essere specificati anche usando una sequenza alternativa '\ddd', dove ddd è il valore decimale del byte in una intervallo 0–255. Per includere caratteri Unicode usando sequenze alternative, è necessario specificare i singoli byte per la codifica UTF-8; in generale, i caratteri Unicode sarà più semplice inserirli direttamente.

Le stringhe laterali possono essere definite usando parentesi quadre. Una parentesi quadra di apertura consiste in una parentesi quadra di apertura con 0 o più segni di uguaglianza con un altra parentesi quadra, per esempio,  , o. La parentesi quadra di apertura dev'essere abbinata alla corrispondente parentesi quadra di chiusura, per esempio,  , o  .. Come caso speciale, se una parentesi quadra di apertura è seguita immediatamente da una nuova riga, allora la nuova riga non è inclusa nella stringa, bensì una nuova riga appena prima della parentesi di chiusura è mantenuta. Le stringhe delimitate da parentesi quadre non sono interpretate come sequenze alternative.

Notare che tutte le stringhe sono considerate vere quando vengono convertite in valori buleani. Questo avviene diversamente da molti altri linguaggi di programmazione, dove la stringa vuota è usualmente considerata falsa.

numeri
Lua ha un unico tipo numerico, che è tipicamente rappresentato internamente come un valore a virgola mobile a doppia precisione. In questo formato, gli interi tra -9007199254740992 e 9007199254740992 (in lettere ±novebiliardisettebilionicentonovantanovemiliardiduecentocinquantaquattromilionisettecentoquarantamilanovecentonovantadue) possono essere rappresentati esattamente, mentre numeri più grandi e numeri con una parte frazionale soffrire di errori di arrotondamento.

Le costanti numeriche vengono specificate usando un punto come un separatore decimale e senza separatori di raggruppamento, per esempio. I numeri possono essere rappresentati anche usando la notazione scientifica esponenziale (usando "e" oppure "E") senza spazi, per esempio,  , o. Gli interi possono anche essere specificati in notazione esadecimale (base 16) usando il prefisso, per esempio.

Sebbene NaN (Non un Numero) e gli infiniti positivi e negativi siano correttamente memorizzati e gestiti, Lua non fornisce i valori letterali corrispondenti. La costante  può essere infinito positivo, una divisione come , od una divisione come   può essere usato per generare rapidamente un NaN.

Notare che tutti i numeri sono considerati veri quando convertiti in valori buleani. Questo diversamente da altri linguaggi di programmazione, dove il numero 0 è normalmente considerato falso. Quando convertito in una stringa, i numeri finiti sono rappresentati in decimali, possibilmente in notazione scientifica (E);  è   e  ; ed gli infiniti sono   e.

tabelle
Le tabelle Lua sono tabelle associative, molto simili alle matrici in PHP ed agli oggetti in JavaScript.

Le tabelle vengono create usando parentesi graffe. La tabella vuota è. Per riempire i campi alla creazione, un elenco di elementi (specificatori di campo) separati da virgole e/o punti e virgola può essere incluso nelle parentesi. Queste prendono una qualsiasi di varie forme:


 * usa il (primo) valore dell’espressione1 come chiave ed il (primo) valore dell’espressione2 come il valore.
 * è equivalente a
 * è pressoché equivalente a, dove i è un intero che parte da 1 ed incrementa ad ogni elemento di questa tabella.
 * Se questo è l'ultimo identificatore di campo e l’espressione ha più valori, vengono utilizzati tutti i valori; altrimenti viene mantenuto solo il primo.

Si accede ai campi di una tabella usando la notazione delle parentesi, per esempio. È possibile accedere alle chiavi stringa nomi che sono valide anche con la notazione del punto, per esempio  è equivalente a. Chiamando una funzione che è un valore nella tabella può usare la notazione dei due punti; per esempio,, che è equivalente a   o.

Una sequenza è una tabella senza valori  per tutti gli interi positivi da 1 a N e valore nullo  per tutti gli interi positivi maggiori di N. Molte funzioni Lua operano solo sequenze, ed ignorano chiavi intere non positive.

Diversamente da molti linguaggi di programmazione come PHP e JavaScript, ogni valore ad eccezione di  e   possono essere usati come una chiave e non viene svolta alcuna conversione. Questi sono tutti validi e distinti:

Similmente, ogni valore ad esclusione di nil può essere memorizzato come valore in una tabella. Memorizzare nil è equivalente a cancellare la chiave della tabella, ed accedendo ad una qualsiasi chiave che non sia stata impostata darà come risultato un valore nil.

Notare che le tabelle non vengono copiate implicitamente in Lua; se una tabella passa come argomento alla funzione e la funzione manipola le chiavi od i valori nella tabella, tali modifiche saranno visibili nel chiamante.

Quando convertito in una stringa, il risultato usuale è, ma può essere sovrascritto usando il metametodo. Anche la tabella vuota è considerata vera come valore buleano.

funzioni
Le funzioni, in Lua, sono valori di prima classe: possono essere creati in modo anonimo, passati per argomenti, assegnati a variabili, e così via.

Le funzioni sono create usando la parola riservata, e chiamate usando parentesi. Zucchero sintattico è disponibile per funzioni con nome, funzioni locali, e funzioni che agiscono come funzioni all'interno di tabella. Vedi dichiarazione di funzione e chiamate di funzione sotto per i dettagli.

Le funzioni Lua sono chiusure, ciò significa che mantengono un riferimento all'ambito in cui sono dichiarate e possono accedere e manipolare le variabili in tale ambito.

Come le tabelle, se una funzione è assegnata ad una variabile differente o passata come un argomento per un'altra funzione, è sempre lo stesso "oggetto funzione" sottostante che sarà chiamata.

Quando convertito in una stringa, il risultato è.



Tipologie non supportate
Il tipo userdata è usato per contenere valori opachi per estensioni a Lua scritte in altri linguaggi di programmazione; per esempio, un userdata può essere usato per maneggiare un puntatore od una struttura scritti in C. Per consentire l'utilizzo di Scribunto in ambienti di allocamento ove non è consentito codice personalizzato, non sono usate estensioni di questo tipo.

Il tipo thread ("forum") rappresenta il riferimento per le co-routine, che non sono disponibili nella pagina di prova di Scribunto.

Metatabella
Una tabella può avere una tabella associata nota come metatable ("metatabella"). I campi nella metatabella da qualche operatore e qualche funzione per specificare un funzionamento differente o ricadente per le tabelle. Alla metatabella per una tabella si può essere accedere usando la funzione getmetatable, ed può essere impostata con la funzione setmetatable.

Quando si accede alle loro metafunzioni, i campi della metatabella sono accessibili come se fossero con rawget.

I campi di Metatabella che influiscono sulla tabella stessa sono:
 * __index
 * Questo è usato quando una tabella accedendo a  restituisce nil. Se il valore di questo campo è una tabella, l'accesso sarà ripetuto in quella tabella, per esempio   (che potrebbe invocare l'indice "__index" della metatabella della tabella). Se il valore di questo campo è una funzione, la funzione sarà chiamata come  . La funzione rawget ignora questo metametodo.


 * __newindex
 * Questo è usato quando si assegna una chiave ad una tabella  dove   restituirebbe nil. Se il alore di questo campo è una tabella, l'assegnazione sarà ripetuta in quella tabella, per esempio   (che potrebbe invocare l'indice "__newindex" della metatabella della tabella). Se il valore di questo campo è una funzione, la funzione sarà chiamata come  . La funzione rawset ignora questo metametodo.


 * __call
 * Questo viene usato quando la sintassi di chiamata della funzione è usata sulla tabella, . Il valore deve essere una funzione, che viene chiamata con qualcosa come.


 * __mode
 * Questo è usato per creare tabelle con riferimenti deboli. Il valore deve essere una stringa. Per impostazioni predefinite, ogni valore che viene usato come chiave o come valore in una tabella non sarà automaticamente raccolto. Ma se questo metacampo contiene la lettera "k", le chiavi possono essere raccolte se non ci sono riferimenti non deboli, e, se contiene la lettera "v", esse possono essere valori; in altri casi, sia le chiavi corrispondenti che i valori corrispondenti sono rimossi dalla tabella. Notare che il funzionamento è indefinito se questo campo è alterato dopo che la tabella è usata come metatabella.

Altri campi di metatabella includono:


 * __add†
 * __sub†
 * __mul†
 * __div†
 * __mod†
 * __pow†
 * __unm
 * __concat†
 * __eq‡
 * __lt‡
 * __le‡
 * __pairs
 * __ipairs
 * __metatable*
 * __tostring

† Per gli operatori binari, Lua esamina prima la metatabella dell'argomento a sinistra (se presente), poi quello a destra quando guarda per usare il metametodo. ‡ Per gli operatori relazionali, il metametodo viene usato solo se la stessa funzione è specificata in entrambe le metatabelle dei parametri. Diverse funzioni anonime, anche con corpo e chiusura identici, potrebbero non essere considerate uguali. * __metatable riguarda sia getmetatable che setmetatable

Nota: in Lua le stringhe sono condivise con un'unica metatabella in cui " " si riferisce alla   della tabella. Questa metatabella è né accessibile in Scribunto, né citata nella stringa della tabella; la stringa della tabella disponibile per i moduli è una copia.

Variabili
Le variabili sono parti di programma che custodiscono valori. Ci sono tre tipi di variabili in Lua: le variabili globali, le variabili locali, ed i campi di tabella.

Un nome rappresenta una variabile globale od una variabile locale (od un argomento di funzione, che è un tipo di variabile locale). Si presume che le variabili siano globali, a meno che vengano dichiarate esplicitamente come variabili locali usando la parola riservata. Ogni variabile a cui non sia stato assegnato un valore, è considerata avere valore nil.

Le variabili globali vengono memorizzate in una tabella Lua standard denominata ambiente; questa tabella è spesso disponibile come variabile globale. È possibile impostare una metatabella per questa tabella delle variabili globali; i metametodi __index e __newindex saranno chiamati per gli accessi e le assegnazioni alle variabili globali proprio come per gli accessi e le assegniazioni ai campi.

L'ambiente per una funzione può essere raggiunto usando la funzione getfenv e può essere cambiato usando la funzione setfenv; in Scribunto, queste funzioni se disponibili a tutti sono molto limitate.

Le variabili locali sono lessicalmente associate; vedi dichiarazione delle variabili locali per dettagli.

Espressioni
Un espressione è qualcosa che ha valori: letterali (numbers, strings,,  ,  ), dichiarazioni di funzioni anonime, costruttori di tabelle, riferimenti variabili, chiamate di funzione, l'espressione vararg, espressioni acchiuse tra parentesi, operatori unari applicati ad espressioni ed espressioni combinate con operatori binari.

La maggior parte delle funzioni ha un valore; le chiamate di funzione l'espressione vararg possono avere qualsiasi numero. Notare che racchiudendo una chiamata di funzioni od un'espressione vararg tra parentesi causerà la perdita di tutti i valori ad eccezione del primo.

Gli elenchi di espressioni sono elenchi di espressionei separate mediante l'uso di virgole. Tutte le espressioni ad eccezione dell'ultima sono forzate ad un valore (eliminando valori aggiuntivi, od usando  se l'espressione non ha valori); tutti i valori dall'ultima espressione sono inclusi tra i valori della lista di espressioni.



Operatori aritmetici
Lua supporta i soliti operatori aritmetici: addizione, sottrazione, moltiplicazione, divisione, modulo, esponenziale e negazione.

Quando tutti gli operandi sono numeri o stringhe con tonumber ritorno non-nil, le operazioni hanno il loro significato abituale.

Se uno degli operandi è una tabella con un definito metametodo, verrà chiamato metametodo.



Operatori relazionali
The relational operators in Lua are,  ,  ,  ,  , and. The result of a relational operator is always a boolean.

Equality first compares the types of its operands; if they are different, the result is false. Then it compares the values: nil, boolean, number, and string are compared in the expected manner. Functions are equal if they refer to the exact same function object;  will return false, as it is comparing two different anonymous functions. Tables are by default compared in the same manner, but this may be changed using the __eq metamethod.

Inequality is the exact negation of equality.

For the ordering operators, if both are numbers or both are strings, they are compared directly. Next, metamethods are checked:


 * uses
 * uses  if available, or if   is available then it is considered equivalent to
 * is considered equivalent to
 * is considered equivalent to

If the necessary metamethods are not available, an error is raised.



Operatori logici
The logical operators are,  , and. All use the standard interpretation where nil and false are considered false and anything else is considered true.

For, if the left operand is considered false then it is returned and the second operand is not evaluated; otherwise the second operand is returned.

For, if the left operand is considered true then it is returned and the second operand is not evaluated; otherwise the second operand is returned.

Per, il risultato è sempre vero o falso.

Note that  and   short circuit. For example,  will only call   if   returns false or nil as its first value.



Operatori concatenati
The concatenation operator is two dots, used as. If both operands are numbers or strings, they are converted to strings and concatenated. Otherwise if a __concat metamethod is available, it is used. Otherwise, an error is raised.

Note that Lua strings are immutable and Lua does not provide any sort of "string builder", so a loop that repeatedly does  will have to create a new string for each iteration and eventually garbage-collect the old strings. If many strings need concatenating, it may be faster to use string.format or to insert all the strings into a sequence and use table.concat at the end.



Operatore di lunghezza
The length operator is, used as. If  is a string, it returns the length in bytes. If  is a sequence table, it returns the length of the sequence.

If  is a table that is not a sequence, the   may return 0 or any value N such that a[N] is not nil and a[N+1] is nil, even if there are non-nil values at higher indexes. For example,



Operatore di precedenza
Lua's operator precedence or order of operations, from highest to lowest:


 * 1) not # - (negazione)
 * 2) + - (subtraction)
 * 3) and
 * or
 * 1) and
 * or
 * 1) and
 * or

Within a precedence level, most binary operators are left-associative, i.e.  is interpreted as. Exponentiation and concatenation are right-associative, i.e.  is interpreted as.

<span id="Function_calls">

Chiamare le funzioni
Lua function calls look like those in most other languages: a name followed by a list of arguments in parentheses:

func (  expression-list  )

As is usual with expression lists in Lua, the last expression in the list may supply multiple argument values.

If the function is called with fewer values in the expression list than there are arguments in the function definition, the extra arguments will have a nil value. If the expression list contains more values than there are arguments, the excess values are discarded. It is also possible for a function to take a variable number of arguments; see Function declarations for details.

Lua also allows direct calling of a function return value, i.e. . If an expression more complex than a variable access is needed to determine the function to be called, a parenthesized expression may be used in place of the variable access.

Lua has syntactic sugar for two common cases. The first is when a table is being used as an object, and the function is to be called as a method on the object. The syntax

table:name (  expression-list  )

is exactly equivalent to

table.name ( table,  expression-list  )

The second common case is Lua's method of implementing named arguments by passing a table containing the name-to-value mappings as the only positional argument to the function. In this case, the parentheses around the argument list may be omitted. This also works if the function is to be passed a single literal string. For example, the calls

func{ arg1 = exp, arg2 = exp } func"string"

Sono equivalenti a

func( { arg1 = exp, arg2 = exp } ) func( "string" )

These may be combined; the following calls are equivalent:

table:name{ arg1 = exp, arg2 = exp } table.name( table, { arg1 = exp, arg2 = exp } )

<span id="Function_declarations">

Dichiarare le funzioni
The syntax for function declaration looks like this:

function nameoptional ( var-listoptional )  block  end

All variables in var-list are local to the function, with values assigned from the expression list in the function call. Additional local variables may be declared inside the block.

When the function is called, the statements in block are executed after local variables corresponding to var-list are created and assigned values. If a return statement is reached, the block is exited and the values of the function call expression are those given by the return statement. If execution reaches the end of the function's block without encountering a return statement, the result of the function call expression has zero values.

Lua functions are lexical closures. A common idiom is to declare "private static" variables as locals in the scope where the function is declared. For example,

A function may be declared to accept a variable number of arguments, by specifying  as the final item in the var-list:

function nameoptional ( var-list, ... )  block  end -- or function nameoptional ( ... )  block  end

Within the block, the varargs expression  may be used, with the result being all the extra values in the function call. For example,

The select function is designed to work with the varargs expression; in particular,  should be used instead of   to count the number of values in the varargs expression, because   may not be a sequence.

Lua provides syntactic sugar to combine function declaration and assignment to a variable; see Function declaration statements for details.

Nota che questo non funzionerà:

local factorial = function ( n ) if n &lt;= 2 then return n     else return n * factorial ( n - 1 ) end end

Since the function declaration is processed before the local variable assignment statement is complete, "factorial" inside the function body refers to the (probably undefined) variable of that name in an outer scope. This problem may be avoided by declaring the local variable first and then assigning it in a subsequent statement, or by using the function declaration statement syntax.

Statements
A statement is the basic unit of execution: one assignment, control structure, function call, variable declaration, etc.

A chunk is a sequence of statements, optionally separated by semicolons. A chunk is basically considered the body of an anonymous function, so it can declare local variables, receive arguments, and return values.

A block is also a sequence of statements, just like a chunk. A block can be delimited to create a single statement:. These may be used to limit the scope of local variables, or to add a  or   in the middle of another block.

Assignments
The variable-list is a comma-separated list of variables; the expression-list is a comma-separated list of one or more expressions. All expressions are evaluated before any assignments are performed, so  will swap the values of a and b.

Local variable declarations
Local variables may be declared anywhere within a block or chunk. The first form, without an expression list, declares the variables but does not assign a value so all variables have nil as a value. The second form assigns values to the local variables, as described in Assignments above.

Note that visibility of the local variable begins with the statement after the local variable declaration. So a declaration like  declares a local variable x and assigns it the value of x from the outer scope. The local variable remains in scope until the end of the innermost block containing the local variable declaration.

Control structures
The while statement repeats a block as long as an expression evaluates to a true value.

The repeat statement repeats a block until an expression evaluates to a true value. Local variables declared inside the block may be accessed in the expression.

This first form of the for loop will declare a local variable, and repeat the block for values from exp1 to exp2 adding exp3 on each iteration. Note that exp3 may be omitted entirely, in which case 1 is used, but non-numeric values such as  and   are an error. All expressions are evaluated once before the loop is started.

This form of the for loop is roughly equivalent to

except that the variables var, limit, and step are not accessible anywhere else. Note that the variable name is local to the block; to use the value after the loop, it must be copied to a variable declared outside the loop.

The second form of the for loop works with iterator functions. As in the first form, the expression-list is evaluated only once before beginning the loop.

This form of the for loop is roughly equivalent to

except that again the variables func, static, and var are not accessible anywhere else. Note that the variables in var-list are local to the block; to use them after the loop, they must be copied to variables declared outside the loop.

Often the expression-list is a single function call that returns the three values. If the iterator function can be written so it only depends on the parameters passed into it, that would be the most efficient. If not, Programming in Lua suggests that a closure be preferred to returning a table as the static variable and updating its members on each iteration.

Executes block1 if exp1 returns true, otherwise executes block2 if exp2 returns true, and block3 otherwise. The  portion may be omitted, and the   portion may be repeated or omitted as necessary.

The return statement is used to return values from a function or a chunk (which is just a function). The expression-list is a comma-separated list of zero or more expressions.

Lua implements tail calls: if expression-list consists of exactly one expression which is a function call, the current stack frame will be reused for the call to that function. This has implication for functions that deal with the call stack, such as  and.

The return statement must be the last statement in its block. If for some reason a return is needed in the middle of a block, an explicit block  may be used.

The break statement is used to terminate the execution of a while, repeat, or for loop, skipping to the next statement after the loop.

The break statement must be the last statement in its block. If for some reason a break is needed in the middle of a block, an explicit block  may be used.

Function calls as statements
A function call may be used as a statement; in this case, the function is being called only for any side effects it may have (e.g. mw.log logs values) and any return values are discarded.

Function declaration statements
Lua provides syntactic sugar to make declaring a function and assigning it to a variable more natural. The following pairs of declarations are equivalent

-- Basic declaration function func( var-list ) block end func = function ( var-list ) block end

-- Local function local function func( var-list ) block end local func; func = function ( var-list ) block end

-- Function as a field in a table function table.func( var-list ) block end table.func = function ( var-list ) block end

-- Function as a method in a table function table:func( var-list ) block end table.func = function ( self, var-list ) block end

Note the colon notation here parallels the colon notation for function calls, adding an implicit argument named  at the beginning of the arguments list.

Error handling
Errors may be "thrown" using the error and assert functions. To "catch" errors, use pcall or xpcall. Note that certain internal Scribunto errors cannot be caught in Lua code.

Garbage collection
Lua performs automatic memory management. This means that you have to worry neither about allocating memory for new objects nor about freeing it when the objects are no longer needed. Lua manages memory automatically by running a garbage collector from time to time to collect all dead objects (that is, objects that are no longer accessible from Lua) and objects that are only reachable via weak references. All memory used by Lua is subject to automatic management: tables, functions, strings, etc.

Garbage collection happens automatically, and cannot be configured from within Scribunto.

<span id="Standard_libraries">

Librerie standard
The standard Lua libraries provide essential services and performance-critical functions to Lua. Only those portions of the standard libraries that are available in Scribunto are documented here.

_G
<span id="_G">

This variable holds a reference to the current global variable table; the global variable  may also be accessed as. Note, however, that there is nothing special about _G itself; it may be reassigned in the same manner as any other variable:

The global variable table may be used just like any other table. For example,

_VERSION
<span id="_VERSION">

A string containing the running version of Lua, e.g. "Lua 5.1".

assert
If  is nil or false, issues an error. In this case,  is used as the text of the error: if nil (or unspecified), the text is "assertion failed!"; if a string or number, the text is that value; otherwise assert itself will raise an error.

If  is any other value, assert returns all arguments including   and.

A somewhat common idiom in Lua is for a function to return a "true" value in normal operation, and on failure return nil or false as the first value and an error message as the second value. Easy error checking can then be implemented by wrapping the call in a call to :

error
Issues an error, with text.

normally adds some information about the location of the error. If  is 1 or omitted, that information is the location of the call to   itself; 2 uses the location of the call of the function that called error; and so on. Passing 0 omits inclusion of the location information.

getfenv
Note this function may not be available, depending on  in the engine configuration.

Returns an environment (global variable table), as specified by :


 * If 1, nil, or omitted, returns the environment of the function calling . Often this will be the same as _G.
 * Integers 2–10 return the environment of functions higher in the call stack. For example, 2 returns the environment for the function that called the current function, 3 returns the environment for the function calling that function, and so on. An error will be raised if the value is higher than the number of function calls in the stack, or if the targeted stack level returned with a tail call.
 * Passing a function returns the environment that will be used when that function is called.

The environments used by all standard library functions and Scribunto library functions are protected. Attempting to access these environments using  will return nil instead.

getmetatable
Returns the metatable of a table. Any other type will return nil.

If the metatable has a  field, that value will be returned instead of the actual metatable.

ipairs
Returns three values: an iterator function, the table, and 0. This is intended for use in the iterator form of :

This will iterate over the pairs ( 1, t[1] ), ( 2, t[2] ), and so on, stopping when t[i] would be nil.

The standard behavior may be overridden by providing an  metamethod. If that metamethod exists, the call to ipairs will return the three values returned by  instead.

next
This allows for iterating over the keys in a table. If  is nil or unspecified, returns the "first" key in the table and its value; otherwise, it returns the "next" key and its value. When no more keys are available, returns nil. It is possible to check whether a table is empty using the expression.

Note that the order in which the keys are returned is not specified, even for tables with numeric indexes. To traverse a table in numerical order, use a numerical for or ipairs.

Behavior is undefined if, when using next for traversal, any non-existing key is assigned a value. Assigning a new value (including nil) to an existing field is allowed.

pairs
Returns three values: an iterator function (next or a work-alike), the table, and nil. This is intended for use in the iterator form of :

This will iterate over the key-value pairs in  just as next would; see the documentation for next for restrictions on modifying the table during traversal.

The standard behavior may be overridden by providing a __pairs metamethod. If that metamethod exists, the call to pairs will return the three values returned by  instead.

pcall
Calls the function  with the given arguments in protected mode. This means that if an error is raised during the call to, pcall will return false and the error message raised. If no error occurs, pcall will return true and all values returned by the call.

In pseudocode,  might be defined something like this:

rawequal
This is equivalent to  except that it ignores any __eq metamethod.

rawget
This is equivalent to  except that it ignores any __index metamethod.

rawset
This is equivalent to  except that it ignores any __newindex metamethod.

select
If  is a number, returns all arguments in   after that index. If  is the string '#', returns the count of arguments in.

In other words,  is something roughly like the following except that it will work correctly even when   contains nil values (see documentation for # and unpack for the problem with nils).

setmetatable
Sets the metatable of a table. may be nil, but must be explicitly provided.

If the current metatable has a __metatable field,  will throw an error.

tonumber
Tries to convert  to a number. If it is already a number or a string convertible to a number, then  returns this number; otherwise, it returns nil.

The optional  (default 10) specifies the base to interpret the numeral. The base may be any integer between 2 and 36, inclusive. In bases above 10, the letter 'A' (in either upper or lower case) represents 10, 'B' represents 11, and so forth, with 'Z' representing 35.

In base 10, the value may have a decimal part, be expressed in E notation, and may have a leading "0x" to indicate base 16. In other bases, only unsigned integers are accepted.

tostring
Converts  to a string. See Data types above for details on how each type is converted.

The standard behavior for tables may be overridden by providing a __tostring metamethod. If that metamethod exists, the call to tostring will return the single value returned by  instead.

type
Returns the type of  as a string: ,  ,  ,  ,  , or.

unpack
Returns values from the given table, something like  would do if written out manually. If nil or not given,  defaults to 1 and   defaults to.

Note that results are not deterministic if  is not a sequence and   is nil or unspecified; see Length operator for details.

xpcall
This is much like, except that the error message is passed to the function   before being returned.

In pseudocode,  might be defined something like this:

debug.traceback
Returns a string with a traceback of the call stack. An optional message string is appended at the beginning of the traceback. An optional level number tells at which stack level to start the traceback.

math.abs
Returns the absolute value of.

math.acos
Returns the arc cosine of  (given in radians).

math.asin
Returns the arc sine of  (given in radians).

math.atan
Returns the arc tangent of  (given in radians).

math.atan2
Returns the arc tangent of  (given in radians), using the signs of both parameters to find the quadrant of the result.

math.ceil
Returns the smallest integer larger than or equal to.

math.cos
Returns the cosine of  (given in radians).

math.cosh
Returns the hyperbolic cosine of.

math.deg
Returns the angle  (given in radians) in degrees.

math.exp
Returns the value $$e^x$$.

math.floor
Returns the largest integer smaller than or equal to.

math.fmod
Returns the remainder of the division of  by   that rounds the quotient towards zero. For example,  yields.

math.frexp
Returns two values  and   such that:


 * If  is finite and non-zero: $$x = m \times 2^e$$,   is an integer, and the absolute value of   is in the range $$[0.5, 1)$$
 * If  is zero:   and   are 0
 * If  is NaN or infinite:   is   and   is not specified

math.huge
The value representing positive infinity; larger than or equal to any other numerical value.

math.ldexp
Returns $$m \times 2^e$$ ( should be an integer).

math.log
Returns the natural logarithm of.

math.log10
Returns the base-10 logarithm of.

math.max
Returns the maximum value among its arguments.

Behavior with NaNs is not specified. With the current implementation, NaN will be returned if  is NaN, but any other NaNs will be ignored.

math.min
Returns the minimum value among its arguments.

Behavior with NaNs is not specified. With the current implementation, NaN will be returned if  is NaN, but any other NaNs will be ignored.

math.modf
Returns two numbers, the integral part of  and the fractional part of. For example,  yields.

math.pi
The value of $$\pi$$.

math.pow
Equivalent to.

math.rad
Returns the angle  (given in degrees) in radians.

math.random
Returns a pseudo-random number.

The arguments  and   may be omitted, but if specified must be convertible to integers.


 * With no arguments, returns a real number in the range $$[0,1)$$
 * With one argument, returns an integer in the range $$[1,m]$$
 * With two arguments, returns an integer in the range $$[m,n]$$

Note that incorrect output may be produced if  or   are less than −2147483648 or greater than 2147483647, or if   is greater than 2147483646.

math.randomseed
Sets  as the seed for the pseudo-random generator.

Note that using the same seed will cause  to output the same sequence of numbers.

math.sin
Returns the sine of  (given in radians).

math.sinh
Returns the hyperbolic sine of.

math.sqrt
Returns the square root of. Equivalent to.

math.tan
Returns the tangent of  (given in radians).

math.tanh
Returns the hyperbolic tangent of.

os.clock
Returns an approximation of the amount in seconds of CPU time used by the program.

os.date

 * Language library's formatDate may be used for more comprehensive date formatting

Returns a string or a table containing date and time, formatted according to. If the format is omitted or nil, "%c" is used.

If  is given, it is the time to be formatted (see  ). Otherwise the current time is used.

If  starts with '!', then the date is formatted in UTC rather than the server's local time. After this optional character, if format is the string "*t", then date returns a table with the following fields:


 * year (full)
 * month (1–12)
 * day (1–31)
 * hour (0–23)
 * min (0–59)
 * sec (0–60, to allow for leap seconds)
 * wday (weekday, Sunday is 1)
 * yday (day of the year)
 * isdst (daylight saving flag, a boolean; may be absent if the information is not available)

If format is not "*t", then date returns the date as a string, formatted according to the same rules as the C function strftime.

os.difftime
Returns the number of seconds from  to.

os.time
Returns a number representing the current time.

When called without arguments, returns the current time. If passed a table, the time encoded in the table will be parsed. The table must have the fields "year", "month", and "day", and may also include "hour" (default 12), "min" (default 0), "sec" (default 0), and "isdst".

require
Loads the specified module.

First, it looks in  to see if the module is already loaded. If so, returns.

Otherwise, it calls each loader in the  sequence to attempt to find a loader for the module. If a loader is found, that loader is called. The value returned by the loader is stored into  and is returned.

See the documentation for  for information on the loaders available.

For example, if you have a module "Module:Giving" containing the following:

You can load this in another module with code such as this:

package.loaded
This table holds the loaded modules. The keys are the module names, and the values are the values returned when the module was loaded.

package.loaders
This table holds the sequence of searcher functions to use when loading modules. Each searcher function is called with a single argument, the name of the module to load. If the module is found, the searcher must return a function that will actually load the module and return the value to be returned by require. Otherwise, it must return nil.

Scribunto provides two searchers:


 * 1) Look in   for the loader function
 * 2) Look in the modules provided with Scribunto for the module name, and if that fails look in the Module: namespace. The "Module:" prefix must be provided.

Note that the standard Lua loaders are not included.

package.preload
This table holds loader functions, used by the first searcher Scribunto includes in package.loaders.

package.seeall
Sets the __index metamethod for  to _G.

Strict library
The strict library is not a normal library; it causes an error to be raised whenever a variable is used and not explicitly scoped as a local variable. It can be enabled with  at the top of your module.

On many Wikimedia wikis this was implemented in "Module:No globals".

String library
In all string functions, the first character is at position 1, not position 0 as in C, PHP, and JavaScript. Indexes may be negative, in which case they count from the end of the string: position -1 is the last character in the string, -2 is the second-last, and so on.

The string library assumes one-byte character encodings. It cannot handle Unicode characters. To operate on Unicode strings, use the corresponding methods in the Scribunto Ustring library.

string.byte
If the string is considered as an array of bytes, returns the byte values for,  , ···,. The default value for  is 1; the default value for  is. Identical to mw.ustring.byte.

string.char
Receives zero or more integers. Returns a string with length equal to the number of arguments, in which each character has the byte value equal to its corresponding argument.

See mw.ustring.char for a similar function that uses Unicode codepoints rather than byte values.

string.find
Looks for the first match of  in the string. If it finds a match, then  returns the offsets in   where this occurrence starts and ends; otherwise, it returns nil. If the pattern has captures, then in a successful match the captured values are also returned after the two indices.

A third, optional numerical argument  specifies where to start the search; its default value is 1 and can be negative. A value of true as a fourth, optional argument  turns off the pattern matching facilities, so the function does a plain "find substring" operation, with no characters in   being considered "magic".

Note that if  is given, then   must be given as well.

See mw.ustring.find for a similar function extended as described in Ustring patterns and where the  offset is in characters rather than bytes.

string.format
Returns a formatted version of its variable number of arguments following the description given in its first argument (which must be a string).

The format string uses a limited subset of the format specifiers:


 * Recognized flags are '-', '+', ' ', '#', and '0'.
 * Integer field widths up to 99 are supported. '*' is not supported.
 * Integer precisions up to 99 are supported. '*' is not supported.
 * Length modifiers are not supported.
 * Recognized conversion specifiers are 'c', 'd', 'i', 'o', 'u', 'x', 'X', 'e', 'E', 'f', 'g', 'G', 's', '%', and the non-standard 'q'.
 * Positional specifiers (e.g. "%2$s") are not supported.

The conversion specifier 'q' is like 's', but formats the string in a form suitable to be safely read back by the Lua interpreter: the string is written between double quotes, and all double quotes, newlines, embedded zeros, and backslashes in the string are correctly escaped when written.

Conversion between strings and numbers is performed as specified in Data types; other types are not automatically converted to strings. Strings containing NUL characters (byte value 0) are not properly handled.

Identical to mw.ustring.format.

string.gmatch
Returns an iterator function that, each time it is called, returns the next captures from  over string. If  specifies no captures, then the whole match is produced in each call.

For this function, a ' ' at the start of a pattern is not magic, as this would prevent the iteration. It is treated as a literal character.

See mw.ustring.gmatch for a similar function for which the pattern is extended as described in Ustring patterns.

string.gsub
Returns a copy of  in which all (or the first , if given) occurrences of the   have been replaced by a replacement string specified by  , which can be a string, a table, or a function. also returns, as its second value, the total number of matches that occurred.

If  is a string, then its value is used for replacement. The character  works as an escape character: any sequence in   of the form  , with d between 1 and 9, stands for the value of the d-th captured substring. The sequence  stands for the whole match, and the sequence   stands for a single.

If  is a table, then the table is queried for every match, using the first capture as the key; if the pattern specifies no captures, then the whole match is used as the key.

If  is a function, then this function is called every time a match occurs, with all captured substrings passed as arguments, in order; if the pattern specifies no captures, then the whole match is passed as a sole argument.

If the value returned by the table query or by the function call is a string or a number, then it is used as the replacement string; otherwise, if it is false or nil, then there is no replacement (that is, the original match is kept in the string).

See mw.ustring.gsub for a similar function in which the pattern is extended as described in Ustring patterns.

string.len
Returns the length of the string, in bytes. Is not confused by ASCII NUL characters. Equivalent to.

See mw.ustring.len for a similar function using Unicode codepoints rather than bytes.

string.lower
Returns a copy of this string with all ASCII uppercase letters changed to lowercase. All other characters are left unchanged.

See mw.ustring.lower for a similar function in which all characters with uppercase to lowercase definitions in Unicode are converted.

string.match
Looks for the first match of  in the string. If it finds one, then  returns the captures from the pattern; otherwise it returns nil. If  specifies no captures, then the whole match is returned.

A third, optional numerical argument  specifies where to start the search; its default value is 1 and can be negative.

See mw.ustring.match for a similar function in which the pattern is extended as described in Ustring patterns and the  offset is in characters rather than bytes.

string.rep
Returns a string that is the concatenation of  copies of the string. Identical to mw.ustring.rep.

string.reverse
Returns a string that is the string  reversed (bytewise).

string.sub
Returns the substring of  that starts at   and continues until  ;   and   can be negative. If  is nil or omitted, it will continue until the end of the string.

In particular, the call  returns a prefix of   with length , and   returns a suffix of   with length.

See mw.ustring.sub for a similar function in which the offsets are characters rather than bytes.

string.upper
Returns a copy of this string with all ASCII lowercase letters changed to uppercase. All other characters are left unchanged.

See mw.ustring.upper for a similar function in which all characters with lowercase to uppercase definitions in Unicode are converted.

Patterns
Note that Lua's patterns are similar to regular expressions, but are not identical. In particular, note the following differences from regular expressions and PCRE:


 * The quoting character is percent, not backslash.
 * Dot always matches all characters, including newlines.
 * No case-insensitive mode.
 * No alternation (the  operator).
 * Quantifiers (, ,  , and  ) may only be applied to individual characters or character classes, not to capture groups.
 * The only non-greedy quantifier is, which is equivalent to PCRE's   quantifier.
 * No generalized finite quantifier (e.g. the  quantifier in PCRE).
 * The only zero-width assertions are,  , and the   "frontier" pattern; assertions such as PCRE's   or   are not present.
 * Patterns themselves do not recognize character escapes such as "\ddd". However, since patterns are strings these sort of escapes may be used in the string literals used to create the pattern-string.

Also note that a pattern cannot contain embedded zero bytes (ASCII NUL, ). Use  instead.

Also see Ustring patterns for a similar pattern-matching scheme using Unicode characters.

Character class
A character class is used to represent a set of characters. The following combinations are allowed in describing a character class:

Pattern items
A pattern item can be


 * a single character class, which matches any single character in the class;
 * a single character class followed by ' ', which matches 0 or more repetitions of characters in the class. These repetition items will always match the longest possible sequence;
 * a single character class followed by ' ', which matches 1 or more repetitions of characters in the class. These repetition items will always match the longest possible sequence;
 * a single character class followed by ' ', which also matches 0 or more repetitions of characters in the class. Unlike ' ', these repetition items will always match the shortest possible sequence;
 * a single character class followed by ' ', which matches 0 or 1 occurrence of a character in the class;
 * , for n between 1 and 9; such item matches a substring equal to the n-th captured string (see below);
 * , where x and y are two distinct characters; such item matches strings that start with x, end with y, and where the x and y are balanced. This means that, if one reads the string from left to right, counting +1 for an x and -1 for a y, the ending y is the first y where the count reaches 0. For instance, the item  matches expressions with balanced parentheses.

Note that frontier patterns were present but undocumented in Lua 5.1, and officially added to Lua in 5.2. The implementation in Lua 5.2.1 is unchanged from that in 5.1.0.
 * , a frontier pattern; such item matches an empty string at any position such that the next character belongs to set and the previous character does not belong to set. The set set is interpreted as previously described. The beginning and the end of the subject are handled as if they were the character '\0'.

Pattern
A pattern is a sequence of pattern items.

A ' ' at the beginning of a pattern anchors the match at the beginning of the subject string. A ' ' at the end of a pattern anchors the match at the end of the subject string. At other positions, ' ' and ' ' have no special meaning and represent themselves.

Captures
A pattern can contain sub-patterns enclosed in parentheses; they describe captures. When a match succeeds, the substrings of the subject string that match captures are stored ("captured") for future use. Captures are numbered according to their left parentheses. For instance, in the pattern, the part of the string matching   is stored as the first capture (and therefore has number 1); the character matching   is captured with number 2, and the part matching   has number 3.

Capture references can appear in the pattern string itself, and refer back to text that was captured earlier in the match. For example,  will match any pair of identical lowercase letters, while   will match any 7-letter palindrome.

As a special case, the empty capture  captures the current string position (a number). For instance, if we apply the pattern  on the string , there will be two captures: 3 and 5.

Table library
Most functions in the table library assume that the table represents a sequence.

The functions,  , and   may be available but are deprecated. Use a for loop with pairs, a for loop with ipairs, and the length operator instead.

table.concat
Given an array where all elements are strings or numbers, returns.

The default value for  is the empty string, the default for   is 1, and the default for   is the length of the table. If  is greater than , returns the empty string.

table.insert
Inserts element  at position   in , shifting up other elements to open space, if necessary. The default value for  is the length of the table plus 1, so that a call   inserts   at the end of table.

Elements up to  are shifted; see Length operator for caveats if the table is not a sequence.

table.maxn
Returns the largest positive numerical index of the given table, or zero if the table has no positive numerical indices.

To do this, it iterates over the whole table. This is roughly equivalent to

table.remove
Removes from  the element at position  , shifting down other elements to close the space, if necessary. Returns the value of the removed element. The default value for  is the length of the table, so that a call   removes the last element of table.

Elements up to  are shifted; see Length operator for caveats if the table is not a sequence.

table.sort
Sorts table elements in a given order, in-place, from  to. If  is given, then it must be a function that receives two table elements, and returns true when the first is less than the second (so that   will be true after the sort). If  is not given, then the standard Lua operator   is used instead.

The sort algorithm is not stable; that is, elements considered equal by the given order may have their relative positions changed by the sort.

<span id="Scribunto_libraries">

Librerie Scribunto
All Scribunto libraries are located in the table.

mw.addWarning
Adds a warning which is displayed above the preview when previewing an edit. is parsed as wikitext.

mw.allToString
Calls tostring on all arguments, then concatenates them with tabs as separators.

mw.clone
Creates a deep copy of a value. All tables (and their metatables) are reconstructed from scratch. Functions are still shared, however.

mw.getCurrentFrame
Returns the current frame object, typically the frame object from the most recent.

mw.incrementExpensiveFunctionCount
Adds one to the "expensive parser function" count, and throws an exception if it exceeds the limit (see ).

mw.isSubsting
Returns true if the current  is being substed, false otherwise. See Returning text above for discussion on differences when substing versus not substing.

mw.loadData
Sometimes a module needs large tables of data; for example, a general-purpose module to convert units of measure might need a large table of recognized units and their conversion factors. And sometimes these modules will be used many times in one page. Parsing the large data table for every  can use a significant amount of time. To avoid this issue,  is provided.

works like, with the following differences:


 * The loaded module is evaluated only once per page, rather than once per  call.
 * The loaded module is not recorded in.
 * The value returned from the loaded module must be a table. Other data types are not supported.
 * The returned table (and all subtables) may contain only booleans, numbers, strings, and other tables. Other data types, particularly functions, are not allowed.
 * The returned table (and all subtables) may not have a metatable.
 * All table keys must be booleans, numbers, or strings.
 * The table actually returned by  has metamethods that provide read-only access to the table returned by the module. Since it does not contain the data directly,   and   will work but other methods, including ,  , and the functions in the Table library, will not work correctly.

The hypothetical unit-conversion module mentioned above might store its code in "Module:Convert" and its data in "Module:Convert/data", and "Module:Convert" would use  to efficiently load the data.

mw.loadJsonData
This is the same as  above, except it loads data from JSON pages rather than Lua tables. The JSON content must be an array or object. See also.

mw.dumpObject
Serializes  to a human-readable representation, then returns the resulting string.

mw.log
Passes the arguments to mw.allToString, then appends the resulting string to the log buffer.

In the debug console, the function  is an alias for this function.

mw.logObject
Calls mw.dumpObject and appends the resulting string to the log buffer. If  is given, it will be added to the log buffer followed by an equals sign before the serialized string is appended (i.e. the logged text will be "prefix = object-string").

Frame object
The frame object is the interface to the parameters passed to, and to the parser.

Note that there is no frame library, and there is no global variable named. A frame object is typically obtained by being passed as a parameter to the function called by, and can also be obtained from.

frame.args
A table for accessing the arguments passed to the frame. For example, if a module is called from wikitext with

then  will return ,   will return  , and   (or  ) will return. It is also possible to iterate over arguments using  or. However, due to how Lua implements table iterators, iterating over arguments will return them in an unspecified order, and there's no way to know the original order as they appear in wikitext.

Note that values in this table are always strings;  may be used to convert them to numbers, if necessary. Keys, however, are numbers even if explicitly supplied in the invocation:  gives string values   and   indexed by numeric keys   and.

As in MediaWiki template invocations, named arguments will have leading and trailing whitespace removed from both the name and the value before they are passed to Lua, whereas unnamed arguments will not have whitespace stripped.

For performance reasons,  uses a metatable, rather than directly containing the arguments. Argument values are requested from MediaWiki on demand. This means that most other table methods will not work correctly, including,  , and the functions in the Table library.

If preprocessor syntax such as template invocations and triple-brace arguments are included within an argument to #invoke, they will not be expanded, after being passed to Lua, until their values are being requested in Lua. If certain special tags written in XML notation, such as,  ,   and  , are included as arguments to #invoke, then these tags will be converted to "strip markers" — special strings which begin with a delete character (ASCII 127), to be replaced with HTML after they are returned from #invoke.

frame:callParserFunction

 * Note the use of named arguments.

Call a parser function, returning an appropriate string. This is preferable to, but whenever possible, native Lua functions or Scribunto library functions should be preferred to this interface.

The following calls are approximately equivalent to the indicated wikitext:

Note that, as with frame:expandTemplate, the function name and arguments are not preprocessed before being passed to the parser function.

frame:expandTemplate

 * Note the use of named arguments.

This is transclusion. The call

frame:expandTemplate{ title = 'template', args = { 'arg1', 'arg2', name = 'arg3' } }

does roughly the same thing from Lua that  does in wikitext. As in transclusion, if the passed title does not contain a namespace prefix it will be assumed to be in the Template: namespace.

Note that the title and arguments are not preprocessed before being passed into the template:

frame:extensionTag
This is equivalent to a call to frame:callParserFunction with function name  and with   prepended to.

frame:getParent
Called on the frame created by, returns the frame for the page that called. Called on that frame, returns nil.

For instance, if the template  contains the code , and a page transcludes that template with the code  , then in Module:ModuleName, calling   and   returns   and  , and calling   and   returns   and  , with   being the first argument in the function call.

frame:getTitle
Returns the title associated with the frame as a string. For the frame created by, this is the title of the module invoked.

frame:newChild

 * Note the use of named arguments.

Create a new Frame object that is a child of the current frame, with optional arguments and title.

This is mainly intended for use in the debug console for testing functions that would normally be called by. The number of frames that may be created at any one time is limited.

frame:preprocess
This expands wikitext in the context of the frame, i.e. templates, parser functions, and parameters such as  are expanded. Certain special tags written in XML-style notation, such as,  ,   and  , will be replaced with "strip markers" &mdash; special strings which begin with a delete character (ASCII 127), to be replaced with HTML after they are returned from.

If you are expanding a single template, use  instead of trying to construct a wikitext string to pass to this method. It's faster and less prone to error if the arguments contain pipe characters or other wikimarkup.

If you are expanding a single parser function, use  for the same reasons.

frame:getArgument
Gets an object for the specified argument, or nil if the argument is not provided.

The returned object has one method,, that returns the expanded wikitext for the argument.

frame:newParserValue
Returns an object with one method,, that returns the result of.

frame:newTemplateParserValue

 * Note the use of named arguments.

Returns an object with one method,, that returns the result of   called with the given arguments.

frame:argumentPairs
Same as. Included for backwards compatibility.

mw.hash.hashValue
Hashes a string value with the specified algorithm. Valid algorithms may be fetched using mw.hash.listAlgorithms.

mw.hash.listAlgorithms
Returns a list of supported hashing algorithms, for use in mw.hash.hashValue.

HTML library
is a fluent interface for building complex HTML from Lua. A mw.html object can be created using.

Functions documented as  are available on the global   table; functions documented as   and   are methods of an mw.html object (see  ).

A basic example could look like this:

mw.html.create
Creates a new mw.html object containing a  html element. You can also pass an empty string or nil as  in order to create an empty mw.html object.

can be a table with the following keys:


 * : Force the current tag to be self-closing, even if mw.html doesn't recognize it as self-closing
 * : Parent of the current mw.html instance (intended for internal usage)

mw.html:node
Appends a child mw.html node to the current mw.html instance. If a nil parameter is passed, this is a no-op. A node is a string representation of an html element.

mw.html:wikitext
Appends an undetermined number of wikitext strings to the mw.html object.

Note that this stops at the first nil item.

mw.html:newline
Appends a newline to the mw.html object.

mw.html:tag
Appends a new child node with the given  to the builder, and returns a mw.html instance representing that new node. The  parameter is identical to that of

mw.html:attr
Set an HTML attribute with the given  and   on the node. Alternatively a table holding name->value pairs of attributes to set can be passed. In the first form, a value of nil causes any attribute with the given name to be unset if it was previously set.

mw.html:getAttr
Get the value of a html attribute previously set using  with the given.

mw.html:addClass
Adds a class name to the node's class attribute. If a nil parameter is passed, this is a no-op.

mw.html:css
Set a CSS property with the given  and   on the node. Alternatively a table holding name->value pairs of properties to set can be passed. In the first form, a value of nil causes any property with the given name to be unset if it was previously set.

mw.html:cssText
Add some raw  to the node's style attribute. If a nil parameter is passed, this is a no-op.

mw.html:done
Returns the parent node under which the current node was created. Like jQuery.end, this is a convenience function to allow the construction of several child nodes to be chained together into a single statement.

mw.html:allDone
Like, but traverses all the way to the root node of the tree and returns it.

Language library
Language codes are described at language code. Many of MediaWiki's language codes are similar to IETF language tags, but not all MediaWiki language codes are valid IETF tags or vice versa.

Functions documented as  are available on the global   table; functions documented as   and   are methods of a language object (see   or  ).

mw.language.fetchLanguageName
The full name of the language for the given language code: native name (language autonym) by default, name translated in target language if a value is given for.

mw.language.fetchLanguageNames
Fetch the list of languages known to MediaWiki, returning a table mapping language code to language name.

By default the name returned is the language autonym; passing a language code for  returns all names in that language.

By default, only language names known to MediaWiki are returned; passing  for   will return all available languages (e.g. from ), while passing   will include only languages having customized messages included with MediaWiki core or enabled extensions. To explicitly select the default,  may be passed.

mw.language.getContentLanguage
Returns a new language object for the wiki's default content language.

mw.language.getFallbacksFor


Returns a list of MediaWiki's fallback language codes for the specified code.

mw.language.isKnownLanguageTag
Returns true if a language code is known to MediaWiki.

A language code is "known" if it is a "valid built-in code" (i.e. it returns true for ) and returns a non-empty string for.

mw.language.isSupportedLanguage
Checks whether any localisation is available for that language code in MediaWiki.

A language code is "supported" if it is a "valid" code (returns true for ), contains no uppercase letters, and has a message file in the currently-running version of MediaWiki.

It is possible for a language code to be "supported" but not "known" (i.e. returning true for ). Also note that certain codes are "supported" despite  returning false.

mw.language.isValidBuiltInCode
Returns true if a language code is of a valid form for the purposes of internal customisation of MediaWiki.

The code may not actually correspond to any known language.

A language code is a "valid built-in code" if it is a "valid" code (i.e. it returns true for ); consists of only ASCII letters, numbers, and hyphens; and is at least two characters long.

Note that some codes are "supported" (i.e. returning true from ) even though this function returns false.

mw.language.isValidCode
Returns true if a language code string is of a valid form, whether or not it exists. This includes codes which are used solely for customisation via the MediaWiki namespace.

The code may not actually correspond to any known language.

A language code is valid if it does not contain certain unsafe characters (colons, single- or double-quotes, slashs, backslashs, angle brackets, ampersands, or ASCII NULs) and is otherwise allowed in a page title.

mw.language.new
Creates a new language object. Language objects do not have any publicly accessible properties, but they do have several methods, which are documented below.

There is a limit on the number of distinct language codes that may be used on a page. Exceeding this limit will result in errors.

mw.language:getCode
Returns the language code for this language object.

mw.language:getFallbackLanguages
Returns a list of MediaWiki's fallback language codes for this language object. Equivalent to.

mw.language:isRTL
Returns true if the language is written right-to-left, false if it is written left-to-right.

mw.language:lc
Converts the string to lowercase, honoring any special rules for the given language.

When the Ustring library is loaded, the mw.ustring.lower function is implemented as a call to.

mw.language:lcfirst
Converts the first character of the string to lowercase, as with lang:lc.

mw.language:uc
Converts the string to uppercase, honoring any special rules for the given language.

When the Ustring library is loaded, the mw.ustring.upper function is implemented as a call to.

mw.language:ucfirst
Converts the first character of the string to uppercase, as with lang:uc.

mw.language:caseFold
Converts the string to a representation appropriate for case-insensitive comparison. Note that the result may not make any sense when displayed.

mw.language:formatNum
Formats a number with grouping and decimal separators appropriate for the given language. Given 123456.78, this may produce "123,456.78", "123.456,78", or even something like "١٢٣٬٤٥٦٫٧٨" depending on the language and wiki configuration.

The  is a table of options, which can be:

Digit transformation may still occur, which may include transforming the decimal separator.
 * : Set true to omit grouping separators and use a dot as the decimal separator.

mw.language:formatDate
Formats a date according to the given format string. If  is omitted, the default is the current time. The value for  must be a boolean or nil; if true, the time is formatted in the wiki's local time rather than in UTC.

The format string and supported values for  are identical to those for the #time parser function from. Note however that backslashes may need to be doubled in a Lua string literal, since Lua also uses backslash as an escape character while wikitext does not:

mw.language:formatDuration
Breaks a duration in seconds into more human-readable units, e.g. 12345 to 3 hours, 25 minutes and 45 seconds, returning the result as a string.

, if given, is a table with values naming the interval units to use in the response. These include ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', and ' '.

mw.language:parseFormattedNumber
This takes a number as formatted by lang:formatNum and returns the actual number. In other words, this is basically a language-aware version of.

mw.language:convertPlural
This chooses the appropriate grammatical form from  (which must be a sequence table) or   based on the number. For example, in English you might use  or   to generate grammatically-correct text whether there is only 1 sock or 200 socks.

The necessary values for the sequence are language-dependent, see localization of magic words and translatewiki's FAQ on PLURAL for some details.

mw.language:convertGrammar

 * Note the different parameter order between the two aliases.  matches the order of the method of the same name on MediaWiki's Language object, while   matches the order of the parser function of the same name, documented at Help:Magic words#Localisation.

This chooses the appropriate inflected form of  for the given inflection code.

The possible values for  and   are language-dependent, see Special:MyLanguage/Help:Magic words and translatewiki:Grammar for some details.

mw.language:gender
Chooses the string corresponding to the gender of, which may be "male", "female", or a registered user name.

mw.language:getArrow
Returns a Unicode arrow character corresponding to :


 * forwards: Either "→" or "←" depending on the directionality of the language.
 * backwards: Either "←" or "→" depending on the directionality of the language.
 * left: "←"
 * right: "→"
 * up: "↑"
 * down: "↓"

mw.language:getDir
Returns "ltr" or "rtl", depending on the directionality of the language.

mw.language:getDirMark
Returns a string containing either U+200E (the left-to-right mark) or U+200F (the right-to-left mark), depending on the directionality of the language and whether  is a true or false value.

mw.language:getDirMarkEntity
Returns "&amp;lrm;" or "&amp;rlm;", depending on the directionality of the language and whether  is a true or false value.

mw.language:getDurationIntervals
Breaks a duration in seconds into more human-readable units, e.g. 12345 to 3 hours, 25 minutes and 45 seconds, returning the result as a table mapping unit names to numbers.

, if given, is a table with values naming the interval units to use in the response. These include ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', and ' '.

Those unit keywords are also the keys used in the response table. Only units with a non-zero value are set in the response, unless the response would be empty in which case the smallest unit is returned with a value of 0.

Message library
This library is an interface to the localisation messages and the MediaWiki: namespace.

Functions documented as  are available on the global   table; functions documented as   and   are methods of a message object (see  ).

mw.message.new
Creates a new message object for the given message. The remaining parameters are passed to the new object's  method.

The message object has no properties, but has several methods documented below.

mw.message.newFallbackSequence
Creates a new message object for the given messages (the first one that exists will be used).

The message object has no properties, but has several methods documented below.

mw.message.newRawMessage
Creates a new message object, using the given text directly rather than looking up an internationalized message. The remaining parameters are passed to the new object's  method.

The message object has no properties, but has several methods documented below.

mw.message.rawParam
Wraps the value so that it will not be parsed as wikitext by.

mw.message.numParam
Wraps the value so that it will automatically be formatted as by. Note this does not depend on the Language library actually being available.

mw.message.getDefaultLanguage
Returns a Language object for the default language.

mw.message:params
Add parameters to the message, which may be passed as individual arguments or as a sequence table. Parameters must be numbers, strings, or the special values returned by mw.message.numParam or mw.message.rawParam. If a sequence table is used, parameters must be directly present in the table; references using the __index metamethod will not work.

Returns the  object, to allow for call chaining.

mw.message:rawParams
Like params, but has the effect of passing all the parameters through mw.message.rawParam first.

Returns the  object, to allow for call chaining.

mw.message:numParams
Like params, but has the effect of passing all the parameters through mw.message.numParam first.

Returns the  object, to allow for call chaining.

mw.message:inLanguage
Specifies the language to use when processing the message. may be a string or a table with a  method (i.e. a Language object).

The default language is the one returned by.

Returns the  object, to allow for call chaining.

mw.message:useDatabase
Specifies whether to look up messages in the MediaWiki: namespace (i.e. look in the database), or just use the default messages distributed with MediaWiki.

The default is true.

Returns the  object, to allow for call chaining.

mw.message:plain
Substitutes the parameters and returns the message wikitext as-is. Template calls and parser functions are intact.

mw.message:exists
Returns a boolean indicating whether the message key exists.

mw.message:isBlank
Returns a boolean indicating whether the message key has content. Returns true if the message key does not exist or the message is the empty string.

mw.message:isDisabled
Returns a boolean indicating whether the message key is disabled. Returns true if the message key does not exist or if the message is the empty string or the string "-".

mw.site.currentVersion
A string holding the current version of MediaWiki.

mw.site.scriptPath
The value of.

mw.site.server
The value of.

mw.site.siteName
The value of.

mw.site.stylePath
The value of.

mw.site.namespaces
Table holding data for all namespaces, indexed by number.

The data available is:


 * id: Namespace number.
 * name: Local namespace name.
 * canonicalName: Canonical namespace name.
 * displayName: Set on namespace 0, the name to be used for display (since the name is often the empty string).
 * hasSubpages: Whether subpages are enabled for the namespace.
 * hasGenderDistinction: Whether the namespace has different aliases for different genders.
 * isCapitalized: Whether the first letter of pages in the namespace is capitalized.
 * isContent: Whether this is a content namespace.
 * isIncludable: Whether pages in the namespace can be transcluded.
 * isMovable: Whether pages in the namespace can be moved.
 * isSubject: Whether this is a subject namespace.
 * isTalk: Whether this is a talk namespace.
 * defaultContentModel: The default content model for the namespace, as a string.
 * aliases: List of aliases for the namespace.
 * subject: Reference to the corresponding subject namespace's data.
 * talk: Reference to the corresponding talk namespace's data.
 * associated: Reference to the associated namespace's data.

A metatable is also set that allows for looking up namespaces by name (localized or canonical). For example, both  and   will return information about the Project namespace.

mw.site.contentNamespaces
Table holding just the content namespaces, indexed by number. See mw.site.namespaces for details.

mw.site.subjectNamespaces
Table holding just the subject namespaces, indexed by number. See mw.site.namespaces for details.

mw.site.talkNamespaces
Table holding just the talk namespaces, indexed by number. See mw.site.namespaces for details.

mw.site.stats
Table holding site statistics. Available statistics are:


 * pages: Number of pages in the wiki.
 * articles: Number of articles in the wiki.
 * files: Number of files in the wiki.
 * edits: Number of edits in the wiki.
 * users: Number of users in the wiki.
 * activeUsers: Number of active users in the wiki.
 * admins: Number of users in group 'sysop' in the wiki.

mw.site.stats.pagesInCategory


Gets statistics about the category. If  has the special value " ", the result is a table with the following properties:


 * all: Total pages, files, and subcategories.
 * subcats: Number of subcategories.
 * files: Number of files.
 * pages: Number of pages.

If  is one of the above keys ("all", "subcats", "files", "pages"), the result is a number with the corresponding value.

Each new category queried will increment the expensive function count.

mw.site.stats.pagesInNamespace
Returns the number of pages in the given namespace (specify by number).

mw.site.stats.usersInGroup
Returns the number of users in the given group.

mw.site.interwikiMap
Returns a table holding data about available interwiki prefixes. If  is the string "local", then only data for local interwiki prefixes is returned. If  is the string "!local", then only data for non-local prefixes is returned. If no filter is specified, data for all prefixes is returned. A "local" prefix in this context is one that is for the same project. For example, on the English Wikipedia, other-language Wikipedias are considered local, while Wiktionary and such are not.

Keys in the table returned by this function are interwiki prefixes, and the values are subtables with the following properties:


 * prefix - the interwiki prefix.
 * url - the URL that the interwiki points to. The page name is represented by the parameter $1.
 * isProtocolRelative - a boolean showing whether the URL is protocol-relative.
 * isLocal - whether the URL is for a site in the current project.
 * isCurrentWiki - whether the URL is for the current wiki.
 * isTranscludable - whether pages using this interwiki prefix are transcludable. This requires scary transclusion, which is disabled on Wikimedia wikis.
 * isExtraLanguageLink - whether the interwiki is listed in.
 * displayText - for links listed in $wgExtraInterlanguageLinkPrefixes, this is the display text shown for the interlanguage link. Nil if not specified.
 * tooltip - for links listed in $wgExtraInterlanguageLinkPrefixes, this is the tooltip text shown when users hover over the interlanguage link. Nil if not specified.

Text library
The text library provides some common text processing functions missing from the String library and the Ustring library. These functions are safe for use with UTF-8 strings.

mw.text.decode
Replaces HTML entities in the string with the corresponding characters.

If boolean  is omitted or false, the only named entities recognized are '&amp;lt;', '&amp;gt;', '&amp;amp;', '&amp;quot;', and '&amp;nbsp;'. Otherwise, the list of HTML5 named entities to recognize is loaded from PHP's function.

mw.text.encode
Replaces characters in a string with HTML entities. Characters '<', '>', '&', '"', and the non-breaking space are replaced with the appropriate named entities; all others are replaced with numeric entities.

If  is supplied, it should be a string as appropriate to go inside brackets in a Ustring pattern, i.e. the "set" in. The default charset is  (the space at the end is the non-breaking space, U+00A0).

mw.text.jsonDecode
Decodes a JSON string. is 0 or a combination (use ) of the flags   and.

Normally JSON's zero-based arrays are renumbered to Lua one-based sequence tables; to prevent this, pass.

To relax certain requirements in JSON, such as no terminal comma in arrays or objects, pass. This is not recommended.

Limitations:


 * Decoded JSON arrays may not be Lua sequences if the array contains null values.
 * JSON objects will drop keys having null values.
 * It is not possible to directly tell whether the input was a JSON array or a JSON object with sequential integer keys.
 * A JSON object having sequential integer keys beginning with 1 will decode to the same table structure as a JSON array with the same values, despite these not being at all equivalent, unless  is used.

mw.text.jsonEncode
Encode a JSON string. Errors are raised if the passed value cannot be encoded in JSON. is 0 or a combination (use ) of the flags   and.

Normally Lua one-based sequence tables are encoded as JSON zero-based arrays; when  is set in , zero-based sequence tables are encoded as JSON arrays.

Limitations:


 * Empty tables are always encoded as empty arrays, not empty objects.
 * Sequence tables cannot be encoded as JSON objects without adding a "dummy" element.
 * To produce objects or arrays with nil values, a tricky implementation of the  metamethod is required.
 * A Lua table having sequential integer keys beginning with 0 will encode as a JSON array, the same as a Lua table having integer keys beginning with 1, unless  is used.
 * When both a number and the string representation of that number are used as keys in the same table, behavior is unspecified.

mw.text.killMarkers
Removes all MediaWiki strip markers from a string.

mw.text.listToText
Joins a list, prose-style. In other words, it's like  but with a different separator before the final item.

The default separator is taken from MediaWiki:comma-separator in the wiki's content language, and the default conjunction is MediaWiki:and concatenated with MediaWiki:word-separator.

Examples, using the default values for the messages:

mw.text.nowiki
Replaces various characters in the string with HTML entities to prevent their interpretation as wikitext. This includes:


 * The following characters:,  ,  ,  ,  ,  ,  ,  ,  ,  ,
 * The following characters at the start of the string or immediately after a newline:,  ,  ,  , space, tab
 * Blank lines will have one of the associated newline or carriage return characters escaped
 * escaped
 * will have one underscore escaped
 * will have the colon escaped
 * A whitespace character following,  , or   will be escaped

mw.text.split
Splits the string into substrings at boundaries matching the Ustring pattern. If  is specified and true,   will be interpreted as a literal string rather than as a Lua pattern (just as with the parameter of the same name for  ). Returns a table containing the substrings.

For example,  would return a table.

If  matches the empty string,   will be split into individual characters.

mw.text.gsplit
Returns an iterator function that will iterate over the substrings that would be returned by the equivalent call to.

mw.text.tag

 * Note the use of named arguments.

Generates an HTML-style tag for.

If  is given, it must be a table with string keys. String and number values are used as the value of the attribute; boolean true results in the key being output as an HTML5 valueless parameter; boolean false skips the key entirely; and anything else is an error.

If  is not given (or is nil), only the opening tag is returned. If  is boolean false, a self-closed tag is returned. Otherwise it must be a string or number, in which case that content is enclosed in the constructed opening and closing tag. Note the content is not automatically HTML-encoded; use mw.text.encode if needed.

For properly returning extension tags such as, use frame:extensionTag instead.

mw.text.trim
Remove whitespace or other characters from the beginning and end of a string.

If  is supplied, it should be a string as appropriate to go inside brackets in a Ustring pattern, i.e. the "set" in. The default charset is ASCII whitespace,.

mw.text.truncate
Truncates  to the specified length in code points, adding   if truncation was performed. If length is positive, the end of the string will be truncated; if negative, the beginning will be removed. If  is given and true, the resulting string including ellipsis will not be longer than the specified length.

The default value for  is taken from MediaWiki:ellipsis in the wiki's content language.

Examples, using the default "..." ellipsis:

mw.text.unstripNoWiki
Replaces MediaWiki &lt;nowiki&gt; strip markers with the corresponding text. Other types of strip markers are not changed.

mw.text.unstrip
Equivalent to.

This no longer reveals the HTML behind special page transclusion, &lt;ref&gt; tags, and so on as it did in earlier versions of Scribunto.

mw.title.equals
Test for whether two titles are equal. Note that fragments are ignored in the comparison.

mw.title.compare
Returns -1, 0, or 1 to indicate whether the title  is less than, equal to, or greater than title.

This compares titles by interwiki prefix (if any) as strings, then by namespace number, then by the unprefixed title text as a string. These string comparisons use Lua's standard  operator.

mw.title.getCurrentTitle
Returns the title object for the current page.

mw.title.new


Creates a new title object.

If a number  is given, an object is created for the title with that page_id. The title referenced will be counted as linked from the current page. If the page_id does not exist, returns nil. The expensive function count will be incremented if the title object created is not for a title that has already been loaded.

If a string  is given instead, an object is created for that title (even if the page does not exist). If the text string does not specify a namespace,  (which may be any key found in  ) will be used. If the text is not a valid title, nil is returned.

mw.title.makeTitle
Creates a title object with title  in namespace , optionally with the specified   and   prefix. may be any key found in. If the resulting title is not valid, returns nil.

Note that, unlike, this method will always apply the specified namespace. For example,  will create an object for the page Template:Module:Foo, while   will create an object for the page Module:Foo.

Title objects
A title object has a number of properties and methods. Most of the properties are read-only.

Note that fields ending with  return titles as string values whereas the fields ending with   return title objects.

.
 * id: The page_id.  if the page does not exist.
 * interwiki: The interwiki prefix, or the empty string if none.
 * namespace: The namespace number.
 * fragment: The fragment (aka section/anchor linking), or the empty string. May be assigned.
 * nsText: The text of the namespace for the page.
 * subjectNsText: The text of the subject namespace for the page.
 * text: The title of the page, without the namespace or interwiki prefixes.
 * prefixedText: The title of the page, with the namespace and interwiki prefixes.
 * fullText: The title of the page, with the namespace and interwiki prefixes and the fragment. Interwiki is not returned if equal to the current.
 * rootText: If this is a subpage, the title of the root page without prefixes. Otherwise, the same as.
 * baseText: If this is a subpage, the title of the page it is a subpage of without prefixes. Otherwise, the same as.
 * subpageText: If this is a subpage, just the subpage name. Otherwise, the same as.
 * canTalk: Whether the page for this title could have a talk page.
 * exists: Whether the page exists. Alias for  for Media-namespace titles. For File-namespace titles this checks the existence of the file description page, not the file itself..
 * file, fileExists: See #File metadata below.
 * isContentPage: Whether this title is in a content namespace.
 * isExternal: Whether this title has an interwiki prefix.
 * isLocal: Whether this title is in this project. For example, on the English Wikipedia, any other Wikipedia is considered "local" while Wiktionary and such are not.
 * isRedirect: Whether this is the title for a page that is a redirect..
 * isSpecialPage: Whether this is the title for a possible special page (i.e. a page in the Special: namespace).
 * isSubpage: Whether this title is a subpage of some other title.
 * isTalkPage: Whether this is a title for a talk page.
 * isSubpageOf( title2 ): Whether this title is a subpage of the given title.
 * inNamespace( ns ): Whether this title is in the given namespace. Namespaces may be specified by anything that is a key found in.
 * inNamespaces( ... ): Whether this title is in any of the given namespaces. Namespaces may be specified by anything that is a key found in.
 * hasSubjectNamespace( ns ): Whether this title's subject namespace is in the given namespace. Namespaces may be specified by anything that is a key found in.
 * contentModel: The content model for this title, as a string..
 * pageLanguage: The page language for this title, as a language object similar to the default returned from  but specific to this page..
 * basePageTitle: The same as.
 * rootPageTitle: The same as.
 * talkPageTitle: The same as, or   if this title cannot have a talk page.
 * subjectPageTitle: The same as.
 * redirectTarget: Returns a title object of the target of the redirect page if the page is a redirect and the page exists, returns  otherwise.
 * protectionLevels: The page's protection levels. This is a table with keys corresponding to each action (e.g.,  and  ). The table values are arrays, the first item of which is a string containing the protection level. If the page is unprotected, either the table values or the array items will be  ..
 * cascadingProtection: The cascading protections applicable to the page. This is a table with keys  (itself a table with keys like   has) and   (an array listing titles where the protections cascade from). If no protections cascade to the  page,   and   will be empty..
 * subPageTitle( text ): The same as.
 * partialUrl: Returns  encoded as it would be in a URL.
 * fullUrl( query, proto ): Returns the full URL (with optional query table/string) for this title. proto may be specified to control the scheme of the resulting url:,  ,   (the default), or.
 * localUrl( query ): Returns the local URL (with optional query table/string) for this title.
 * canonicalUrl( query ): Returns the canonical URL (with optional query table/string) for this title.
 * getContent: Returns the (unparsed) content of the page, or  if there is no page. The page will be recorded as a transclusion.

Title objects may be compared using relational operators. will return.

Since people find the fact surprising, note that accessing any expensive field on a title object records a "link" to the page (as shown on Special:WhatLinksHere, for example). Using the title object's  method or accessing the   field records it as a "", and accessing the title object's   or   fields records it as a "".

File metadata
Title objects representing a page in the File or Media namespace will have a property called. This is a table, structured as follows:


 * exists: Whether the file exists. It will be recorded as an image usage. The  property on a Title object exists for backwards compatibility reasons and is an alias for this property. If this is , all other file properties will be.
 * width: The width of the file. If the file contains multiple pages, this is the width of the first page.
 * height: The height of the file. If the file contains multiple pages, this is the height of the first page.
 * pages: If the file format supports multiple pages, this is a table containing tables for each page of the file; otherwise, it is . The # operator can be used to get the number of pages in the file. Each individual page table contains a width and height property.
 * size: The size of the file in bytes.
 * mimeType: The MIME type of the file.
 * length: The length (duration) of the media file in seconds. Zero for media types which do not support length.

Expensive properties
The properties,  ,  , and   require fetching data about the title from the database. For this reason, the expensive function count is incremented the first time one of them is accessed for a page other than the current page. Subsequent accesses of any of these properties for that page will not increment the expensive function count again.

Other properties marked as expensive will always increment the expensive function count the first time they are accessed for a page other than the current page.

mw.uri.encode
Percent-encodes the string. The default type,, encodes spaces using '+' for use in query strings;   encodes spaces as %20; and   encodes spaces as '_'.

Note that the "WIKI" format is not entirely reversible, as both spaces and underscores are encoded as '_'.

mw.uri.decode
Percent-decodes the string. The default type,, decodes '+' to space;   does not perform any extra decoding; and   decodes '_' to space.

mw.uri.anchorEncode
Encodes a string for use in a MediaWiki URI fragment.

mw.uri.buildQueryString
Encodes a table as a URI query string. Keys should be strings; values may be strings or numbers, sequence tables, or boolean false.

mw.uri.parseQueryString
Decodes the query string  to a table. Keys in the string without values will have a value of false; keys repeated multiple times will have sequence tables as values; and others will have strings as values.

The optional numerical arguments  and   can be used to specify a substring of   to be parsed, rather than the entire string. is the position of the first character of the substring, and defaults to 1. is the position of the last character of the substring, and defaults to the length of the string. Both  and   can be negative, as in string.sub.

mw.uri.canonicalUrl
Returns a URI object for the canonical URL for a page, with optional query string/table.

mw.uri.fullUrl
Returns a URI object for the full URL for a page, with optional query string/table.

mw.uri.localUrl
Returns a URI object for the local URL for a page, with optional query string/table.

mw.uri.new
Constructs a new URI object for the passed string or table. See the description of URI objects for the possible fields for the table.

mw.uri.validate
Validates the passed table (or URI object). Returns a boolean indicating whether the table was valid, and on failure a string explaining what problems were found.

URI object
The URI object has the following fields, some or all of which may be nil:


 * protocol: String protocol/scheme
 * user: String user
 * password: String password
 * host: String host name
 * port: Integer port
 * path: String path
 * query: A table, as from mw.uri.parseQueryString
 * fragment: String fragment.

The following properties are also available:
 * userInfo: String user and password
 * hostPort: String host and port
 * authority: String user, password, host, and port
 * queryString: String version of the query table
 * relativePath: String path, query string, and fragment

will give the URI string.

Methods of the URI object are:

mw.uri:parse
Parses a string into the current URI object. Any fields specified in the string will be replaced in the current object; fields not specified will keep their old values.

mw.uri:clone
Makes a copy of the URI object.

mw.uri:extend
Merges the parameters table into the object's query table.

Ustring library
The ustring library is intended to be a direct reimplementation of the standard String library, except that the methods operate on characters in UTF-8 encoded strings rather than bytes.

Most functions will raise an error if the string is not valid UTF-8; exceptions are noted.

mw.ustring.maxPatternLength
The maximum allowed length of a pattern, in bytes.

mw.ustring.maxStringLength
The maximum allowed length of a string, in bytes.

mw.ustring.byte
Returns individual bytes; identical to string.byte.

mw.ustring.byteoffset
Returns the byte offset of a character in the string. The default for both  and   is 1. may be negative, in which case it counts from the end of the string.

The character at  == 1 is the first character starting at or after byte  ; the character at   == 0 is the first character starting at or before byte. Note this may be the same character. Greater or lesser values of  are calculated relative to these.

mw.ustring.char
Much like string.char, except that the integers are Unicode codepoints rather than byte values.

mw.ustring.codepoint
Much like string.byte, except that the return values are codepoints and the offsets are characters rather than bytes.

mw.ustring.find
Much like string.find, except that the pattern is extended as described in Ustring patterns and the  offset is in characters rather than bytes.

mw.ustring.format
Identical to string.format. Widths and precisions for strings are expressed in bytes, not codepoints.

mw.ustring.gcodepoint
Returns three values for iterating over the codepoints in the string. defaults to 1, and  to -1. This is intended for use in the iterator form of :

mw.ustring.gmatch
Much like string.gmatch, except that the pattern is extended as described in Ustring patterns.

mw.ustring.gsub
Much like string.gsub, except that the pattern is extended as described in Ustring patterns.

mw.ustring.isutf8
Returns true if the string is valid UTF-8, false if not.

mw.ustring.len
Returns the length of the string in codepoints, or nil if the string is not valid UTF-8.

See string.len for a similar function that uses byte length rather than codepoints.

mw.ustring.lower
Much like string.lower, except that all characters with lowercase to uppercase definitions in Unicode are converted.

If the Language library is also loaded, this will instead call lc on the default language object.

mw.ustring.match
Much like string.match, except that the pattern is extended as described in Ustring patterns and the  offset is in characters rather than bytes.

mw.ustring.rep
Identical to string.rep.

mw.ustring.sub
Much like string.sub, except that the offsets are characters rather than bytes.

mw.ustring.toNFC
Converts the string to Normalization Form C. Returns nil if the string is not valid UTF-8.

mw.ustring.toNFD
Converts the string to Normalization Form D. Returns nil if the string is not valid UTF-8.

mw.ustring.upper
Much like string.upper, except that all characters with uppercase to lowercase definitions in Unicode are converted.

If the Language library is also loaded, this will instead call uc on the default language object.

Ustring patterns
Patterns in the ustring functions use the same syntax as the String library patterns. The major difference is that the character classes are redefined in terms of Unicode character properties:


 *  : represents all characters with General Category "Letter".
 *  : represents all characters with General Category "Control".
 *  : represents all characters with General Category "Number, decimal digit".
 *  : represents all characters with General Category "Lowercase Letter".
 *  : represents all characters with General Category "Punctuation".
 *  : represents all characters with General Category "Separator", plus tab, linefeed, carriage return, vertical tab, and form feed.
 *  : represents all characters with General Category "Uppercase Letter".
 *  : represents all characters with General Category "Letter" or "Decimal Number".
 *  : adds fullwidth character versions of the hex digits.

Like in String library patterns,  ,  ,  ,  ,  ,  ,    here represent the complementary set ("all characters without given General Category").

In all cases, characters are interpreted as Unicode characters instead of bytes, so ranges such as, patterns such as  , and quantifiers applied to multibyte characters will work correctly. Empty captures will capture the position in code points rather than bytes.

Loadable libraries
These libraries are not included by default, but if needed may be loaded using.

bit32
This emulation of the Lua 5.2  library may be loaded using

bit32 = require( 'bit32' )

The bit32 library provides bitwise operations on unsigned 32-bit integers. Input numbers are truncated to integers (in an unspecified manner) and reduced modulo 232 so the value is in the range 0 to 232−1; return values are also in this range.

When bits are numbered (as in bit32.extract), 0 is the least-significant bit (the one with value 20) and 31 is the most-significant (the one with value 231).

bit32.band
Returns the bitwise AND of its arguments: the result has a bit set only if that bit is set in all of the arguments.

If given zero arguments, the result has all bits set.

bit32.bnot
Returns the bitwise complement of.

bit32.bor
Returns the bitwise OR of its arguments: the result has a bit set if that bit is set in any of the arguments.

If given zero arguments, the result has all bits clear.

bit32.btest
Equivalent to

bit32.bxor
Returns the bitwise XOR of its arguments: the result has a bit set if that bit is set in an odd number of the arguments.

If given zero arguments, the result has all bits clear.

bit32.extract
Extracts  bits from , starting with bit. Accessing bits outside of the range 0 to 31 is an error.

If not specified, the default for  is 1.

bit32.replace
Replaces  bits in , starting with bit  , with the low   bits from. Accessing bits outside of the range 0 to 31 is an error.

If not specified, the default for  is 1.

bit32.lshift
Returns the number  shifted   bits to the left. This is a logical shift: inserted bits are 0. This is generally equivalent to multiplying by 2undefined.

Note that a displacement over 31 will result in 0.

bit32.rshift
Returns the number  shifted   bits to the right. This is a logical shift: inserted bits are 0. This is generally equivalent to dividing by 2undefined.

Note that a displacement over 31 will result in 0.

bit32.arshift
Returns the number  shifted   bits to the right. This is an arithmetic shift: if  is positive, the inserted bits will be the same as bit 31 in the original number.

Note that a displacement over 31 will result in 0 or 4294967295.

bit32.lrotate
Returns the number  rotated   bits to the left.

Note that rotations are equivalent modulo 32: a rotation of 32 is the same as a rotation of 0, 33 is the same as 1, and so on.

bit32.rrotate
Returns the number  rotated   bits to the right.

Note that rotations are equivalent modulo 32: a rotation of 32 is the same as a rotation of 0, 33 is the same as 1, and so on.

libraryUtil
This library contains methods useful when implementing Scribunto libraries. It may be loaded using

libraryUtil = require( 'libraryUtil' )

libraryUtil.checkType
Raises an error if  does not match. In addition, no error will be raised if  is nil and   is true.

is the name of the calling function, and  is the position of the argument in the argument list. These are used in formatting the error message.

libraryUtil.checkTypeMulti
Raises an error if  does not match any of the strings in the array.

This is for arguments that have more than one valid type.

libraryUtil.checkTypeForIndex
Raises an error if  does not match.

This is intended for use in implementing a  metamethod.

libraryUtil.checkTypeForNamedArg
Raises an error if  does not match. In addition, no error will be raised if  is nil and   is true.

This is intended to be used as an equivalent to  in methods called using Lua's "named argument" syntax,.

libraryUtil.makeCheckSelfFunction
This is intended for use in implementing "methods" on object tables that are intended to be called with the  syntax. It returns a function that should be called at the top of these methods with the  argument and the method name, which will raise an error if that   object is not.

This function will generally be used in a library's constructor function, something like this:

luabit
The luabit library modules "bit" and "hex" may be loaded using

bit = require( 'luabit.bit' ) hex = require( 'luabit.hex' )

Note that the bit32 library contains the same operations as "luabit.bit", and the operations in "luabit.hex" may be performed using  and.

The luabit module "noki" is not available, as it is entirely useless in Scribunto. The luabit module "utf8" is also not available, as it was considered redundant to the Ustring library.

ustring
The pure-Lua backend to the Ustring library may be loaded using

ustring = require( 'ustring' )

In all cases the Ustring library should be used instead, as that replaces many of the slower and more memory-intensive operations with callbacks into PHP code.

Extension libraries
Some MediaWiki extensions provide additional Scribunto libraries. These are also located in the table, usually in the table  , however, they are only present when certain extensions are installed (in addition to the Scribunto extension itself).

Such extensions use Scribunto provided hooks:
 * ScribuntoExternalLibraries
 * ScribuntoExternalLibraryPaths

Writing Scribunto libraries provides information on how such libraries can be developed to provide Lua interfaces for MediaWiki extensions.

The following libraries are planned, or are in Gerrit pending review.


 * (none at this time)

mw.wikibase
provides access to localizable structured data, most notably Wikidata. See md_docs_topics_lua.html and.

mw.wikibase.lexeme
WikibaseLexeme provides access to Wikibase Lexeme entities. This is supported by Wikidata:Lexicographical data.

mw.wikibase.mediainfo
WikibaseMediaInfo provides access to Wikibase MediaInfo entities. See. This is supported by Structured Data on Commons. See Commons:Structured data/Lua.

mw.bcmath
BCmath provides arbitrary-precision arithmetic to Lua modules. See BCmath documentation via "LDoc" link at Extension:BCmath.

mw.smw
Semantic Scribunto provides native support for the Scribunto extension to Semantic MediaWiki extension.

mw.ext.data
JsonConfig provides access to localizable tabular and map data. See Extension:JsonConfig/Tabular. Tabular Data and GeoJSON Map Data is supported in Commons "Data:" namespace.

mw.ext.cargo
Cargo provides a means to query its data store from Lua. See Extension:Cargo/Other features.

mw.ext.cattools
CategoryToolbox provides a means to check from Lua if a certain page belongs to a category. Is is experimental and not enabled on public WikiMedia wikis.

mw.ext.FlaggedRevs
FlaggedRevs provides a means to access the stability settings of a page from Lua.

mw.ext.TitleBlacklist
TitleBlacklist provides a means to test and obtain information about blacklisted page naming entries from Lua.

mw.ext.ParserFunctions
ParserFunctions provides a means to evaluate a parser function expressions from Lua.

mw.ext.articlePlaceholder
ArticlePlaceholder provides a means to override default Wikibase renderings from Lua. See Extension:ArticlePlaceholder/Module:AboutTopic.

mw.ext.externalData
ExternalData provides a means to get structured data from Internet from Lua. See Extension:External Data/Lua.

mw.ext.seo
WikiSEO provides a means to set SEO Data for the current page. See Extension:WikiSEO.

<span id="Differences_from_standard_Lua">

Changed functions
The following functions have been modified:
 * setfenv
 * getfenv: May not be available, depending on the configuration. If available, attempts to access parent environments will fail.
 * getmetatable: Works on tables only to prevent unauthorized access to parent environments.
 * tostring: Pointer addresses of tables and functions are not provided. This is to make memory corruption vulnerabilities more difficult to exploit.
 * pairs
 * ipairs: Support for the __pairs and __ipairs metamethods (added in Lua 5.2) has been added.
 * pcall
 * xpcall: Certain internal errors cannot be intercepted.
 * require: Can fetch certain built-in modules distributed with Scribunto, as well as modules present in the Module namespace of the wiki. To fetch wiki modules, use the full page name including the namespace. Cannot otherwise access the local filesystem.

Removed functions and packages
The following packages are mostly removed. Only those functions listed are available:
 * package.*: Filesystem and C library access has been removed. Available functions and tables are:
 * package.loaded
 * package.preload
 * package.loaders: Loaders which access the local filesystem or load C libraries are not present. A loader for Module-namespace pages is added.
 * package.seeall


 * os.*: There are some insecure functions in here, such as os.execute, which can't be allowed. Available functions are:
 * os.clock
 * os.date
 * os.difftime
 * os.time


 * debug.*: Most of the functions are insecure. Available functions are:
 * debug.traceback

The following functions and packages are not available:
 * collectgarbage
 * module
 * coroutine.*: No application is known for us, so it has not been reviewed for security.
 * dofile
 * loadfile
 * io.*, file.*: Allows local filesystem access, which is insecure.
 * load
 * loadstring: These were omitted to allow for static analysis of the Lua source code. Also, allowing these would allow Lua code to be added directly to article and template pages, which was not desired for usability reasons.
 * print: This was discussed on wikitech-l and it was decided that it should be omitted in favour of return values, to improve code quality. If necessary, mw.log may be used to output information to the debug console.
 * string.dump: May expose private data from parent environments.

Additional caveats
Attempting to do so will cause undefined behavior. This includes (but is not limited to) returning such data structures from the module called by  and passing such data structures as parameters to Scribunto library functions that are implemented as callbacks into PHP. Such data structures may be used freely within Lua, including as the return values of modules loaded with.
 * Referential data structures: Circular data structures and data structures where the same node may be reached by more than one path cannot be correctly sent to PHP.

<span id="Writing_Scribunto_libraries">

Scrivere librerie Scribunto
This information is useful to developers writing additional Scribunto libraries, whether for inclusion in Scribunto itself or for providing an interface for their own extensions.

A Scribunto library will generally consist of five parts:


 * The PHP portion of the library.
 * The Lua portion of the library.
 * The PHP portion of the test cases.
 * The Lua portion of the test cases.
 * The documentation.

Existing libraries serve as a good example.

Library
The PHP portion of the library is a class that must extend. See the documentation for that class for implementation details. In the Scribunto extension, this file should be placed in, and a mapping added to. Other extensions should use the ScribuntoExternalLibraries hook. In either case, the key should match the Lua module name ("mw.name" for libraries in Scribunto, or "mw.ext.name" for extension libraries).

The Lua portion of the library sets up the table containing the functions that can be called from Lua modules. In the Scribunto extension, the file should be placed in. This file should generally include boilerplate something like this:

The module in  (load this with  ) contains some functions that may be helpful.

Be sure to run the Scribunto test cases with your library loaded, even if your library doesn't itself provide any test cases. The standard test cases include tests for things like libraries adding unexpected global variables. Also, if the library is loaded with PHP, any upvalues that its Lua functions have will not be reset between #invoke's. Care must be taken to ensure that modules can't abuse this to transfer information between #invoke's.

Test cases
The Scribunto extension includes a base class for test cases,, which will run the tests against both the LuaSandbox and LuaStandalone engines. The library's test case should extend this class, and should not override. In the Scribunto extension, the test case should be in  and added to the array in  (in  ); extensions should add the test case in their own   hook function, probably conditional on whether   is set.

Most of the time, all that is needed to make the test case is this:

class ClassNameTest extends Scribunto_LuaEngineTestBase { protected static $moduleName = 'ClassNameTest'; function getTestModules { return parent::getTestModules + array(             'ClassNameTest' => __DIR__ . '/ClassNameTests.lua';          ); } }

This will load the file  as if it were the page "Module:ClassNameTests", expecting it to return an object with the following properties:


 * count: Integer, number of tests
 * provide( n ): Function that returns three values:, the name of test  , and a string that is the expected output for test.
 * run( n ): Function that runs test  and returns one string.

If  is declared as shown, "Module:TestFramework" is available which provides many useful helper methods. If this is used,  would look something like this:

local testframework = require 'Module:TestFramework' return testframework.getTestProvider( {    -- Tests go here  } )

Each test is itself a table, with the following properties:


 * name: The name of the test.
 * func: The function to execute.
 * args: Optional table of arguments to pass to the function.
 * expect: Results to expect.
 * type: Optional "type" of the test, default is "Normal".

The type controls the format of  and how   is called. Included types are:


 * Normal:  is a table of return values, or a string if the test should raise an error.   is simply called.
 * Iterator:  is a table of tables of return values.   is called as with an iterated for loop, and each iteration's return values are accumulated.
 * ToString: Like "Normal", except each return value is passed through.

Test cases in another extension
There are (at least) two ways to run PHPUnit tests:

If your extension's test class names all contain a unique component (e.g. the extension's name), the  option may be used to run only your extension's tests.
 * 1) Run phpunit against core, allowing the tests/phpunit/suites/ExtensionsTestSuite.php to find the extension's tests using the  hook.
 * 1) Run phpunit against the extension directory, where it will pick up any file ending in "Test.php".

Either of these will work fine if Scribunto is loaded in LocalSettings.php. And it is easy for method #1 to work if Scribunto is not loaded, as the UnitTestsList hook can easily be written to avoid returning the Scribunto test when is not set.

But Jenkins uses method #2. For Jenkins to properly run the tests, you will need to add Scribunto as a dependency for your extension. See for an example of how this is done.

If for some reason you need the tests to be able to run using method #2 without Scribunto loaded, one workaround is to add this check to the top of your unit test file:

Documentation
Modules included in Scribunto should include documentation in the Scribunto libraries section above. Extension libraries should include documentation in a subpage of their own extension page, and link to that documentation from the Extension libraries subsection above.

<span id="See_also">

Altro

 * Lua (programming language)

Licenza
This manual is derived from the Lua 5.1 reference manual, which is available under the MIT license.

This derivative manual may also be copied under the terms of the same license.