Extension:Loops

The Loops extension provides parser functions for performing loops.

Usage

#while

{{#while}} performs a loop (i.e. it repeatedly parses a given wiki markup block statement) so long as the condition mark-up evaluates to non-whitespace.

{{
  #while:
  | <condition text>
  | <block statement>
}}

Examples

The wiki markup:

{{ #vardefine: i | 0 }}{{
  #while:
  | {{ #ifexpr: {{ #var: i }} < 5 | true }}
  |<nowiki/>
* {{ #var: i }}{{ #vardefine: i | {{ #expr: {{ #var: i }} + 1 }} }}
}}

produces the following:

• 0
• 1
• 2
• 3
• 4

{{#while}} can also be used in a template to simulate a numbered array. If the page "Template:Loops Test" contains

{{
  #vardefine: i | 0
}}{{
  #while:
  | {{{ arg{{#var: i }} |}}}
  |<nowiki/>
* {{{ arg{{#var: i }} }}}{{
    #vardefine: i
    | {{ #expr: {{ #var: i }} + 1 }}
  }}
}}

then the wiki-markup

{{Loops Test
|arg0=zero
|arg1=one
|arg2=two
|arg3=three
|arg4=four
}}

produces

• zero
• one
• two
• three
• four

It's important to note that whitespace, including newlines, tabs, and spaces, is stripped from the beginning and end of all the arguments of these parser functions. If this is not desirable, adding any non-whitespace characters (including the HTML encoding for a whitespace character  ) will prevent further stripping (hence the <nowiki/> tags in the above examples).

#dowhile

{{#dowhile}} performs exactly like {{#while}}, with the exception that the block statement is guaranteed to be parsed and displayed (if it results in displayable text) at least once. This is done before the condition text is evaluated.

#loop

{{
  #loop: <variable name>
  | <starting value>
  | <number of loops to be performed>
  | <wiki markup>
}}

{{#loop}} repeatedly parses and displays <wiki markup> a number of times equal to the absolute value of <number of loops to be performed>. <Starting value> is placed in a variable (accessible by {{#var:}} parser function) using the name <variable name>. After each loop, the variable is incremented by one if <number of loops to be performed> is positive, or decremented by one if <number of loops to be performed> is negative.

Note: From all loop functions, #loop should have the best performance since there is no condition which has to be expanded and validated for each cycle.

Examples

The following code:

{{#loop: varname
  | 4
  | 4
  | <nowiki/>
* This is round {{#var:varname}} and we have {{#expr: 7- {{#var:varname}}}} more to go
}}

produces

• This is round 4 and we have 3 more to go
• This is round 5 and we have 2 more to go
• This is round 6 and we have 1 more to go
• This is round 7 and we have 0 more to go

#forargs

{{#forargs}} is to be used in templates. It takes arguments that are passed to the template and puts them in variables accessible by {{#var:}} parser function.

{{
  #forargs: <prefix>
  | <key>
  | <value>
  | <block statement>
}}

This function iterates through each argument whose name begins with <prefix>. With each iteration it puts the argument name minus <prefix> into <key> as if calling {{#vardefine: <key> }}. It then takes the value of the argument and puts it into <value> in a similar method. The block statement is then expanded. The block statement may contain {{#var: <key> }} and {{#var: <value> }} to access the stored arguments.

Example

If the page "Template:Loops Test" contains

{{
  #forargs: arg
  | key
  | value
  | <nowiki/>
* {{#var: key}} = {{#var: value}}
}}

then the wiki markup

{{Loops Test
| arg1=val1
| spam=spammity
| arg5=val5
| argument=value
}}

produces

• 1 = val1
• 5 = val5
• ument = value

#fornumargs

{{
  #fornumargs: <key>
  | <value>
  | <block statement>
}}

{{#fornumargs}} performs similarly to {{#forargs}} with two major differences: It doesn't take a prefix argument, and it only works on numbered arguments whether they're explicitly numbered:

{{Template | 1=one | 2=two }}

or implicitly numbered:

{{Template | one | two }}

Mixing these methods in a single template call may cause values to get overwritten, so be careful.

Examples

If "Template:Loops Test" is edited to contain:

{{
  #fornumargs: number
  | value
  | <nowiki/>
* {{#var: number}} = {{#var: value}}
}}

then

{{Loops Test
  | Apricot
  | B = Bolognese
  | Caramel slice
  | 5 = Eclair
}}

will result in

• 1 = Apricot
• 2 = Caramel slice
• 5 = Eclair