Red marquis at 22:11, 22 December 2010

2010-12-22T22:11:44Z

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<includeonly>{{{{{|safesubst:}}}{{{{{|safesubst:}}}#switch:{{{{{|safesubst:}}}#ifexpr:{{{1}}}|p1|p2}}|p1=p1|p2=p2|if/errmsg}}|{{{2}}}|{{{3|}}}|{{{1}}}}}</includeonly><noinclude><div class="template-documentation" style="margin-top:1em;">{{#if:defaultnotblank|<div style="padding-bottom:3px; border-bottom:1px solid #aaa; margin-bottom:1ex;">
<span style="font-size:150%">Documentation</span></div>}}
{{Documentation subpage}}
With this template [[mw:Help:Extension:ParserFunctions|#ifexpr]] can be used in a way such that it does not [[Help:Newlines_and_spaces#Stripping_on_expansion|strip spaces and newlines]] from the "then" and "else" part.

==Usage==
*<code><nowiki>{{ifexpr|2<3| p | q }}</nowiki></code> gives "{{ifexpr|2<3| p | q }}"
*<code><nowiki>{{ifexpr|2>3| p | q }}</nowiki></code> gives "{{ifexpr|2>3| p | q }}"
*<code><nowiki>{{ifexpr|2{{=}}3| p | q }}</nowiki></code> gives "{{ifexpr|2{{=}}3| p | q }}"
*<code><nowiki>{{ifexpr||1=2=3| p | q }}</nowiki></code> gives "{{ifexpr||1=2=3| p | q }}"
*<code><nowiki>{{ifexpr||1=7=7| ok true | no }}</nowiki></code> gives "{{ifexpr||1=7=7| ok true | no }}"
*<code><nowiki>{{ifexpr||1=3*4<=10+1| ok| oh no}}</nowiki></code> gives "{{ifexpr||1=3*4<=10+1| ok| oh no}}"
Compare:
*<code><nowiki>{{#ifexpr:2<3| p | q }}</nowiki></code> gives "{{#ifexpr:2<3| p | q }}"

Note that, unlike parser functions, templates require writing equals signs in values of unnamed parameters by using double-braces, as <code><nowiki>{{=}}</nowiki></code>. So, to allow "=" (or "<=" or ">=") then use the named parameter 1, as in: 1={{{x}}}>=7.

For full substitution, simply use {{cnw|subst:}} or {{cnw|safesubst:}}. If the condition contains a parser function, template, or variable, that should be substituted too. Optionally the "then" or "else" part can also be substituted.

Error messages (examples):

*<code><nowiki>{{ifexpr|1234>e3|1|0}}</nowiki></code> gives {{ifexpr|1234>e3|1|0}}
*<code><nowiki>{{#ifexpr:1234>e3|1|0}}</nowiki></code> gives {{#ifexpr:1234>e3|1|0}}, for e3.
*<code><nowiki>{{#ifexpr:1234>1e3|1|0}}</nowiki></code> gives {{#ifexpr:1234>1e3|1|0}}, because 1,234 > 1e3 (1,000).

==Expansion depth limit==
13 levels allowed:

<code><nowiki>{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|a}}}}}}}}}}}}}}}}}}}}}}}}}}</nowiki></code> gives {{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|a}}}}}}}}}}}}}}}}}}}}}}}}}}

<code><nowiki>{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|a}}}}}}}}}}}}}}}}}}}}}}}}}}}}</nowiki></code> gives {{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|{{ifexpr|1|a}}}}}}}}}}}}}}}}}}}}}}}}}}}}

==Internal technical details==
For evaluating the condition the template uses the actual parser functions; however, not directly with p and q, because this strips spaces and newlines from them, but with index values 1 and 2. The result can be 1, 2, or an error message. Using a switch these are converted to p1, p2, and if/errmsg, respectively. The template with the applicable name is called ([[Template:P1]], [[Template:P2]], or [[Template:If/errmsg]]), with as parameters p, q, and {{{1}}}. Templates p1 and p2 ignore {{{1}}}; template if/errmsg is only called in the case of a wrong expression {{{1}}}; it ignores p and q and uses {{{1}}} for display in the error message.

==See also==
*[[m:Template:Ifexpr]]
{{refs}}

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Template:Ifexpr - Revision history

Red marquis at 22:11, 22 December 2010