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| With this template [[mw:Help:Extension:ParserFunctions|#ifexpr]] can be used in a way such that it does not strip spaces and newlines from the "then" and "else" part.
| | <noinclude><!-- |
| | | -============================================================= |
| ==Usage== | | - If/errmsg - Show message for Template:If or Template:Ifexpr |
| *<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 }}"
| | - (see NOTES at bottom) |
| *<code><nowiki>{{ifexpr|2{{=}}3| p | q }}</nowiki></code> gives "{{ifexpr|2{{=}}3| p | q }}"
| | - |
| *<code><nowiki>{{ifexpr|7{{=}}7| ok true | no }}</nowiki></code> gives "{{ifexpr|7{{=}}7| ok true | no }}"
| | --></noinclude><br> |
| *<code><nowiki>{{ifexpr|3*4<{{=}}10+1| ok| oh no}}</nowiki></code> gives "{{ifexpr|3*4<{{=}}10+1| ok| oh no}}"
| | <font color="#FF5511">'''ERROR: invalid parameters for [[Template:{{{t|Ifexpr}}}]]''':<br> <nowiki>{{</nowiki>{{{t|Ifexpr}}}...|{{{3}}}|{{{1}}}|{{{2}}}<nowiki>}}</nowiki><br> Check for invalid numbers, or parameter 1 must be empty when using "1=" format.</font><noinclude> |
| Compare:
| | <!-- |
| *<code><nowiki>{{#ifexpr:2<3| p | q }}</nowiki></code> gives "{{#ifexpr:2<3| p | q }}"
| | -------------------------------------------------------------- |
| | | --NOTES |
| 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.
| | -- [ These comments are skipped by <noinclude> so they will |
| | | -- be omitted & not sent in a formatted Internet page. ] |
| For full substitution, simply use <code>subst:</code> or <code>safesubst:</code>. 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.
| | -- |
| | | -- NOTE A1: This template displays advisory messages for |
| Error messages (examples):
| | -- either the Template:If or Template:Ifexpr. |
| | | -- |
| *<code><nowiki>{{ifexpr|1234>e3|1|0}}</nowiki></code> gives {{ifexpr|1234>e3|1|0}}
| | -- NOTE S2: This template can be subst-substituted by using |
| *<code><nowiki>{{#ifexpr:1234>e3|1|0}}</nowiki></code> gives {{#ifexpr:1234>e3|1|0}}, for e3.
| | -- {{subst:str_range|...}} to save only the results, or |
| *<code><nowiki>{{#ifexpr:1234>1e3|1|0}}</nowiki></code> gives {{#ifexpr:1234>1e3|1|0}}, because 1,234 > 1e3 (1,000).
| | -- {{{{{|safesubst:}}}str_range}} using blank parameter. |
| | | -- |
| ==Expansion depth limit==
| | -------------------------------------------------------------- |
| During 2011-2012, the nesting limit of {Ifexpr} was 12 nested structures (this is one of the template limits for the MediaWiki parser). For example, nesting 13 times can cause an error:
| | --HISTORY: |
| | | --03Dec10 Created to extract substring range with real spaces. |
| * <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>
| | --03Dec10 Put NOTES comments to explain template coding. |
| | | --03Dec10 Put HISTORY comments to log major changes (not typos). |
| * '''Result:''' <nowiki>{{safesubst:{{</nowiki><span style="color:#C12222">'''Expansion depth limit exceeded'''</span><nowiki>|p1=p1|p2=p2|if/errmsg}}|a||1}}</nowiki>
| | --03Dec10 New parameter {t} template name (default: t=Ifexpr). |
| The expansion-depth error occurs when exceeding the depth limit of nested markup, typically 41 levels of nested templates or if-else structures, during 2009-2012.
| | --03Dec10 Added "Check for invalid numbers, or...". |
| | | -- |
| ==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.
| | {{documentation}} |
| | | [[Category:General wiki templates]] |
| ==Dependencies==
| |
| This template depends on the existence of
| |
| * {{t|p1}}
| |
| * {{t|p2}}
| |
| * {{t|p3}}
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| * {{t|if/errmsg}}
| |
| | |
| ==See also==
| |
| *[[m:Template:Ifexpr]]
| |
| | |
| | |
| <noinclude>
| |
| {{Wikipedia-deleted|
| |
| * Patrick
| |
| * Wikid77
| |
| }}
| |
| </noinclude> | | </noinclude> |