Help:Extension:ParserFunctions/zh

扩展提供11个額外的解析器函数以补充MediaWiki固有的“”. （它有可能会配置到增加的解析器函数以支持运行：这些字符串函数已在记载. ） 所有的解析器函数由下列的表格提供.

#expr
这个函数计算并返回数学表达式的结果. 这个函数也通过 函数中在有效.



右表依优先级列出了支持的运算符，运算符的详细说明请见帮助:计算. 运算结果的精度和格式受服务器操作系统及语言设置影响可能存在差异.

使用布尔代数时，0表示 ，其他任何非0数值（无论正负）均表示 ：



空表达式返回空值，错误的表达式返回错误信息，使用 函数检查错误：



置于数字前或数字后的加减号是有意义的，会被视为正负号而不会报错：



注意：使用魔术字输出数值时，首先要将其格式化以去除逗号，获得纯数字. 例如： 输出，而期望的输出值是0，使用 便可以实现. 对于某些语言，格式化数字尤为重要. 例如孟加拉语中， 的输出结果是৩০,০৬১.



四舍五入
a round b是指将a四舍五入至(1/10)b的整数倍.

向上、向下取整分别使用 或.

字符串
表达式函数只用于仅含有数字和运算符号的表达式，而字母字符串和其它符号不在此列. 若需要比较字符串，可以用替代.



#if
这个函数判断一个字符串是否为空. 只包含空格的字符串被视为空字符串.





这个函数首先判断参数1是否为空. 如果参数1不为空，则输出参数2. 如果参数1为空或只包含空白内容（空格、换行等），则输出参数3.



字符串内容会被处理为纯文本，因此数学表达式不会被计算：



最后一个参数（false）可以被忽略：



该函数可嵌套. 为了做到这一点，嵌套内层的#if函数需要按规则完整填写所有参数以符合#if的参数形式. 一般至多可嵌套7层，该数也可能为wiki自身限制和内存限制而有变动.

你可以在#if条件句中以字符串变量代替测试字符串. 在这里，你需要在变量名的后面加上 (分隔符)以正确引用字符串. （因此如果参数没有值，则计算结果为一个空字符串而非" "）



在这里 获得更多关于解释器函数中变量的相关例子.

#ifeq
这个函数判断两个輸入字符串是否相同，並根據結果輸出兩個字符串的其中一個. 如果需要更多的比較和輸出字符串，請考慮使用.



如果两个字符串均为数字，则函数会进行数值的比较：



否则函数会进行文本的比较（大小写敏感）：


 * →  （对比上面没有引号的例子）
 * →  （对比上面带有 的例子，會先回傳一個有效的整數）
 * →  （对比上面没有引号的例子）
 * →  （对比上面带有 的例子，會先回傳一個有效的整數）

作为例子，考虑一个已经存在着的 ，该模板利用解析器来選擇兩個標準時間，short和long. 它以参数作为第一个输入来比较字符串“short”–这没有约定顺序，但是如果参数在第一个则更容易理解. 模板代码定义为:



会产生如下结果：


 * → 20
 * → 40
 * → 40

#iferror
这个函数以一个字符串为输入，然后在两条预选结果中取其一而返回. 函数认定为 当且仅当作为输入参数的字符串在解释时返回的结果中含有一个 的HTML对象，而其中可用来认定结果的包括其他的解释器函数（比如 ， 和 ）的错误，模板错误（比如模板循环和模板递归），还有一些其它的解释器“软错误”.



待返回字符串参数可以省略. 若省略 （正确）字符串参数，则在 （测试字符串）不出错的情况下函数将返回被测字符串本身. 若省略 （错误）字符串参数，则函数将在被测字符串出错时返回空字符串：


 * → &zwnj;
 * → &zwnj;
 * → &zwnj;
 * → &zwnj;
 * → &zwnj;
 * → &zwnj;

#ifexpr
此函数会判断数学表达式并根据其布尔值结果返回对应的字符串：



这里 输入串将原封不动的作为上面 的参数进行调用，且表达式运算符是通用的，返回值也将作为布尔表达式进行处理.

输入表达式为空时将视为 ：



如上面所提，0将视为 ，非零值将视为 ，因此这个函数与下面的仅用 和 的表述等价：



除了下面这种情况：所输入表达式为空或者是一个错误表达式（空串会返回一条错误信息，而它不等于0，所以在后者我们会得到 ）.



相对的



两个待选返回值都不是必填的. 当表达式判断对应的分支返回值被省略时，函数不会给出输出：



Boolean operators of equality or inequality operators are supported.



#ifexist
这个函数将一组字符串作为输入，并翻译成页面标题，然后根据在本地wiki上是否存在该页面而返回对应的值.



只要页面存在就会判定为 （真值），即便那个页面看上去是空白的（比如像是分类链接或者是解释页之类的却不包含任何可视内容的页面），或者是，或者它就是空白页. 当且仅当页面是红链时判定为 （假值），包括那些曾经存在却被删除的页面.



函数在对应模块被安装时认定为 ，对的判定则取决于本地软件自身.



如果一个页面使用了 来检查目标页面，则这个检查页面将出现在被检查页面的里. 所以如果本页面（）使用了代码 ，那么/Foo将列出.

若wiki有其在使用的对应的共享媒体库， 就可用于检查一个文件是否在媒体库中，而不仅仅只是在wiki本体上检查：



如果文件有一个已创建的对应的本地描述页面，上面的结果将全部是exists.

不会对跨wiki链接起作用.

ifexist 限制
被视为“高开销（expensive）解析器函数”，每个页面调用这类函数的次数（包括包含于嵌入式模板的函数）存在一个限制. 当达到该限制时，对于多出该限制的 函数，无论其目标页面是否存在，函数只会自动返回错误值false，且该页面会被分类到Category:中. 可能因您的wiki内容的语言而异.

在某些案例中，在css中，利用选择器 （以选出链接到不存在的页面的链接）或者是 （以选出已存在页面的链接），是可以达到模仿ifexist的效果的. 另外，控制 可以调整对高开销解析器函数数量的限制，如果有需要，也可以增加页面LocalSettings.php中的限制值.

ifexisit和需要的页面
一个不存在的页面被#ifexist检测后会被计数在待创建页面中. 请参阅了解原因，并查看w:Template:Linkless exists以了解解决方法.

#rel2abs
这个函数将文件的相对路径转换为绝对路径.



在输入项 中，可以使用以下类型的句法：


 * → 本级路径
 * → 回到上一级
 * → 向下一级进入子目录/foo

若 没有指定，将默认的填入函数所在页面的绝对路径：



形如 或 的不合理的句法将被忽略. 连用至多两个句点(如: )是可以的，语句会被正确的分割成可成功执行的情况：



#switch
See also : w:Help:Switch parser function

该函数将一个输入值同若干个测试样例（test cases）做比较，如果找到匹配，返回有关联的字符串.

例如：



含有部分嵌入包含标记的 # switch会影响到能让不熟悉模板代码的编辑者查看和编辑可配置元素的配置文件.

默认
如果 不能与任何 匹配，则返回 ，即默认结果:



在这种语法中，默认返回值必须是函数的最后一个参数，而且不能包含原始等号（不帶 的等號）. 否则，就会解析为样例比较，无匹配的样例时不显示文本. 这是因为默认值没有定义（是空的）. 如果有样例匹配，则返回关联的字符串.



你也可以将 字符串设为'' 从而清楚地声明默认值.

这种方式声明的默认结果可以放在函数的任何地方：



如果 参数被省略，且没有找到匹配，则不返回结果：



分组结果
该函数允许存在“fall through”现象，多个 字符串返回相同的 字符串，从而减少重复.

在本例中，第二、三、四个分支都会返回 ，第六和第七个分支都会返回. 上述案例中，最后一个参数中的“ ”可以省略.

带有参数使用
该函数允许将参数用作测试字符串. 在本例中，不必将管道符放在参数名称后面，因为你不太可能需要选择字符串“ ”作为样例. (（如果没有管道符，且参数不存在或没有值，则参数就会显示为这样. ） 参见. )



上面的例子中，如果 等于 ，函数返回. If it equals, the function will return. If the parameter is empty or does not exist, the function will return.

As in the section above, cases can be combined to give a single result.



Here, if  equals ,   or  , the function will return. If it equals, the function will return. If the parameter is empty or does not exist, the function will return.

Additionally, the default result can be omitted if you do not wish to return anything if the test parameter value does not match any of the cases.



In this case, the function returns an empty string unless  exists and equals   or , in which case it returns   or  , respectively.

This has the same effect as declaring the default result as empty.



If for some reason you decide to set a case as " ", the function will return that case's result when the parameter doesn't exist or doesn't have a value. The parameter would have to exist and have a value other than the string " " to return the function's default result.


 * (when  doesn't exist or is empty):
 * →  Foo 
 * (when  has the value " "):
 * →  Bar 
 * (when  has the value " "):
 * →  Foo 

In this hypothetical case, you would need to add the pipe to the parameter.

比较行为
如同 那样，若被比较串和测试条件串都是数字串的，那么将之按照数字进行比较；反之若存在一个非纯数字串，都会按照字符串比较规则进行：





一个 串可以是空的：



顺序的，只要有一个 匹配中了，其它的都会被忽略：



原始等号
"Case"测试条件串中不能包含原始等号. 如果需要在比较串中加入等号，可以使用仅包含一个等号的模板=来代替 ，或者是用HTML标识码 来代替.

例如：





替换#ifeq
可以用于迭代深度.

例如：



等效于



也就是线性的深度迭代判断：

但同时，用switch代替嵌套的IF语句有可能会使语句变得更为复杂，甚至弄巧成拙，例如下面的这个例子，IF语句构成了一棵对称的决策树，相应对称的部分已经用缩进和注释标齐：

#time
This parser function takes a date and/or time (in the Gregorian calendar) and formats it according to the syntax given. A date/time object can be specified; the default is the value of the magic word  – that is, the time the page was last rendered into HTML.



The list of accepted formatting codes is given in the table to the right. Any character in the formatting string that is not recognized is passed through unaltered; this applies also to blank spaces (the system does not need them for interpreting the codes). There are also two ways to escape characters within the formatting string: In addition, the digraph  is interpreted as a single literal "x".
 * 1) A backslash followed by a formatting character is interpreted as a single literal character
 * 2) Characters enclosed in double quotes are considered literal characters, and the quotes are removed.



The  can be in any format accepted by PHP's strtotime function. Both absolute (eg ) and relative (eg  ) times are accepted.


 * &rarr; 
 * &rarr; 
 * &rarr; 
 * &rarr; 
 * &rarr; 
 * &rarr; 
 * &rarr; 

The  in ISO 639-3 (?) allows the string to be displayed in the chosen language



The  parameter specifies if the date/time object refers to the local timezone or to UTC.

This is a boolean parameters: its value is determined by casting the value of the argument (see the official PHP documentation for details on how string are cast to boolean values).

See the following examples for details:





If you've calculated a Unix timestamp, you may use it in date calculations by pre-pending an  symbol.



Full or partial absolute dates can be specified; the function will "fill in" parts of the date that are not specified using the current values:



4位數字總是被解讀為年分，而不是小時和分鐘：



6位數字盡量被解讀為小時、分鐘、秒，不然會被解讀為錯誤（而不是年分和月分）：


 * →  輸入被視為時間而不是年+月代碼.
 * →  雖然19:60:09不是有效時間，但196009不被解讀為1960年9月.

該函數執行一定數量的日期算數：



調用的格式字符串的總長度限制為6000個字符.

时区问题
There is a bug in this #time parser function (more specifically in PHP DateTime) that does not allow the passing-in of non-integers as relative time zone offsets. This issue does not apply when using an on-the-hour time zone, such as EDT. For example:


 * &rarr;

However, India is on a +5.5 hours time offset from UTC, and thus using its time zone will not normally allow the correct calculation of a relative time zone offset. Here's what happens:


 * &rarr;

To workaround this issue, simply convert the time into minutes or seconds, like this:


 * &rarr;
 * &rarr;

(Tim Starling, the developer of this function, provided the exact syntax for this solution.)

#timel
This function is identical to, when the   parameter is set to  , so it always uses the local time of the wiki (as set in ).

Syntax of the function is:





For instance, see the following examples:





#titleparts
This function separates a page title into segments based on slashes, then returns some of those segments as output.



If the number of segments to return parameter is not specified, it defaults to "0", which returns all the segments from the first segment to return (included). If the first segment to return parameter is not specified or is "0", it defaults to "1":


 * →  See also.
 * →  See also.

Negative values are accepted for both values. Negative values for the number of segments to return parameter effectively 'strips' segments from the end of the string. Negative values for the first segment to return translates to "start with this segment counting from the right":


 * →  Strips one segment from the end of the string. 参见.
 * →   Strips all 4 segments from the end of the string
 * →   Strips 5 segments from the end of the string (more than exist)
 * →   Returns last segment. 参见.
 * →   Strips one segment from the end of the string, then returns the second segment and beyond
 * →   Start copying at the second last element; strip one segment from the end of the string

Before processing, the pagename parameter is HTML-decoded: if it contains some standard HTML character entities, they will be converted to plain characters (internally encoded with UTF-8, i.e. the same encoding as in the MediaWiki source page using this parser function).


 * For example, any occurrence of,  , or   in pagename will be replaced by.
 * No other conversion from HTML to plain text is performed, so HTML tags are left intact at this initial step even if they are invalid in page titles.

Then the decoded pagename is canonicalized into a standard page title supported by MediaWiki, as much as possible:


 * 1) All underscores are automatically replaced with spaces:
 * →  Not bah_boo, despite the underscore in the original.
 * 1) The string is split a maximum of 25 times; further slashes are ignored and the 25th element will contain the rest of the string. The string is also limited to 255 characters, as it is treated as a page title:
 * If for whatever reason you needed to push this function to its limit, although very unlikely, it is possible to bypass the 25 split limit by nesting function calls:
 * 1) Finally the first substring is capitalized according to the capitalization settings of the local wiki (if that substring also starts by a local namespace name, that namespace name is also normalized).
 * 1) Finally the first substring is capitalized according to the capitalization settings of the local wiki (if that substring also starts by a local namespace name, that namespace name is also normalized).
 * 1) Finally the first substring is capitalized according to the capitalization settings of the local wiki (if that substring also starts by a local namespace name, that namespace name is also normalized).

{{Warning|1= Certain characters that are illegal in a page title will cause #titleparts to not parse the string:


 * → {{#titleparts: {one/two} | 1 | 1 }}. Does not produce the expected: {one
 * → {{#titleparts: page/123 | 1 | 2 }}. Does not work because brackets are illegal in page titles and this parser function does not process links embedded in its input pagename parameter, even when they use the MediaWiki syntax, or any other HTML or MediaWiki tags.
 * → "{{#titleparts: red/#00FF00/blue| 1 | 3 }}". Does not work because "#" is also illegal in page titles.

}}

StringFunctions
All of these functions are integrated from the StringFunctions extension, but are only available if an administrator sets   in.

All of these functions operate in O(n) time complexity, making them safe against DoS attacks.

#len
The #len function returns the length of the given string. The syntax is:

The return value is always a number of characters in the source string (after expansions of template invocations, but before conversion to HTML). If no string is specified, the return value is zero.

#pos
The #pos function returns the position of a given search term within the string. The syntax is:

The offset parameter, if specified, tells a starting position where this function should begin searching.

If the search term is found, the return value is a zero-based integer of the first position within the string.

If the search term is not found, the function returns an empty string.

#rpos
The #rpos function returns the last position of a given search term within the string. The syntax is:

If the search term is found, the return value is a zero-based integer of its last position within the string.

If the search term is not found, the function returns -1.

#sub
The #sub function returns a substring from the given string. The syntax is:

The start parameter, if positive (or zero), specifies a zero-based index of the first character to be returned.

Example: returns.

returns.

If the start parameter is negative, it specifies how many characters from the end should be returned.

Example: returns.

The length parameter, if present and positive, specifies the maximum length of the returned string.

Example: returns.

If the length parameter is negative, it specifies how many characters will be omitted from the end of the string.

Example: returns.

If the start parameter is negative, it specifies how many characters from the end should be returned. The length parameter, if present and positive, specifies the maximum length of the returned string from the starting point.

Example: returns.

#count
The #count function returns the number of times a given substring appears within the provided text.

#replace
The #replace function returns the given string with all occurrences of a search term replaced with a replacement term.

If the search term is unspecified or empty, a single space will be searched for.

If the replacement term is unspecified or empty, all occurrences of the search term will be removed from the string.

Currently the syntax doesn't provide a switch to toggle case-sensitivity setting. But you may make use of magic words of formatting as a workaround. (e.g. your_string_here ) For example, if you want to remove the word "Category:" from the string regardless of its case, you may type:
 * Case-insensitive replace :

But the disadvantage is that the output will become all lower-case. If you want to keep the casing after replacement, you have to use multiple nesting levels (i.e. multiple replace calls) to achieve the same thing.

#explode
The #explode function splits the given string into pieces and then returns one of the pieces. The syntax is:

The delimiter parameter specifies a string to be used to divide the string into pieces. This delimiter string is then not part of any piece, and when two delimiter strings are next to each other, they create an empty piece between them. If this parameter is not specified, a single space is used. The limit parameter is available in ParserFunctions only, not the standalone StringFunctions version, and allows you to limit the number of parts returned, with all remaining text included in the final part.

The position parameter specifies which piece is to be returned. Pieces are counted from 0. If this parameter is not specified, the first piece is used (piece with number 0). When a negative value is used as position, the pieces are counted from the end. In this case, piece number -1 means the last piece. Examples:


 * returns
 * returns
 * returns
 * returns

The return value is the position-th piece. If there are fewer pieces than the position specifies, an empty string is returned.

#urldecode
converts the escape characters from an 'URL encoded' string string back to readable text. The syntax is:

Notes:
 * This function works by directly exposing PHP's urldecode function.
 * A character-code-reference can be found at www.w3schools.com.
 * The opposite,, has been integrated into MediaWiki as of version 1.18; for examples, see.
 * urldecode was merged from Stringfunctions in 2010, by commit 1b75afd18d3695bdb6ffbfccd0e4aec064785363

Limits
This module defines three global settings:


 * $wgStringFunctionsLimitSearch
 * $wgStringFunctionsLimitReplace
 * $wgStringFunctionsLimitPad

These are used to limit some parameters of some functions to ensure the functions operate in O(n) time complexity, and are therefore safe against DoS attacks.

$wgStringFunctionsLimitSearch
This setting is used by #pos, #rpos, #replace, and #explode. All these functions search for a substring in a larger string while they operate, which can run in O(n*m) and therefore make the software more vulnerable to DoS attacks. By setting this value to a specific small number, the time complexity is decreased to O(n).

This setting limits the maximum allowed length of the string being searched for.

The default value is 30 multibyte characters.

$wgStringFunctionsLimitReplace
This setting is used by #replace. This function replaces all occurrences of one string for another, which can be used to quickly generate very large amounts of data, and therefore makes the software more vulnerable to DoS attacks. This setting limits the maximum allowed length of the replacing string.

The default value is 30 multibyte characters.

替代
Parser functions can be substituted by prefixing the hash character with :


 * → the code   will be inserted in the wikitext since the page exists.

Substitution does not work within ; you can use &hellip;  for this purpose.

重定向
Especially   could be handy in  to pages including dates, but this does not work.

在表格中逸出的管道符
Parser functions will mangle syntax and pipe characters, treating all the raw pipe characters as parameter dividers. To avoid this, most wikis used a template    :! with its contents only a raw pipe character, since MW 1.24 a  replaced this kludge. This 'hides' the pipe from the MediaWiki parser, ensuring that it is not considered until after all the templates and variables on a page have been expanded. It will then be interpreted as a table row or column separator. Alternatively, raw HTML table syntax can be used, although this is less intuitive and more error-prone.

You can also escape the pipe character for display as a plain, uninterpreted character using an HTML entity:.

剥离空格
Whitespace, including newlines, tabs, and spaces, is stripped from the beginning and end of all the parameters of these parser functions. If this is not desirable, comparison of strings can be done after putting them in quotation marks.



To prevent the trimming of then and else parts, see m:Template:If. Some people achieve this by using &lt; &gt;  &lt; /nowiki &gt; instead of spaces.


 * → foofoo
 * → foofoo

However, this method can be used to render a single whitespace character only, since the parser squeezes multiple whitespace characters in a row into one.




 * || → || foofoo 
 * }

In this example, the  style is used to force the whitespace to be preserved by the browser, but even with it the spaces are not shown. This happens because the spaces are stripped by the software, before being sent to the browser.

It is possible to workaround this behavior replacing whitespaces with  (breakable space) or   (non-breakable space), since they are not modified by the software:


 * →  foofoo 
 * → foofoo

参见

 * m:幫助:計算
 * m:幫助:換行及空格
 * m:Help:Comparison between ParserFunctions syntax and TeX syntax
 * , an (incomplete) list of parser functions added by core and extensions.
 * Module:String已废弃的
 * Parser functions for Wikibase (the extensions that enables Wikidata): d:Special:MyLanguage/Wikidata:How to use data on Wikimedia projects
 * Module:String已废弃的
 * Parser functions for Wikibase (the extensions that enables Wikidata): d:Special:MyLanguage/Wikidata:How to use data on Wikimedia projects
 * Parser functions for Wikibase (the extensions that enables Wikidata): d:Special:MyLanguage/Wikidata:How to use data on Wikimedia projects