Template:For loop

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This template implements a foreach loop. This is a legacy template, and exists for reasons of backwards compatibility. If you need to use a for loop, it is almost always better to implement it as a Lua module.

This template calls a user specified template once for each of a list of values. A named parameter is passed with the value from the list of the current iteration with a possible prefix and/or a postfix attached. In addition to the variable parameter, fixed parameters can be specified to be passed with each iteration. The first unnamed parameter is output between calls to the user specified template.

Usage

{{for loop|<!-- separator, whitespace is preserved -->|
    call    = template to call
  | pc1n    = name  of the 1st static parameter passed to the called template
  | pc1v    = value of the 1st static parameter passed to the called template
  | pc2n    = name  of the 2nd static parameter passed to the called template
  | pc2v    = value of the 2nd static parameter passed to the called template
  | pc3n    = name  of the 3rd static parameter passed to the called template
  | pc3v    = value of the 3rd static parameter passed to the called template
<!-- More fixed parameters passed to the called template can be inserted as needed -->
  | pv      = parameter name used to pass to the called template to which is
                assigned the variable values with prefix prepended and postfix apended.
  | prefix  = static prefix prepended to each of the variable values
  | postfix = static postfix appended to each of the variable values
  | list of variable values with separator "|", whitespace is stripped
     (empty parameter values work in the regular way, they are ''not'' ignored like undefined ones)
}}

The separator is the first unnamed parameter, allowing it to start and/or end with newlines and spaces. The separator is output between calls to the template named in |call=. It is not output after the last call to that template. The separator parameter is prior to the value list. If a value in the list contains an equals sign, use use {{=}} (see Help:Template). If you do not use {{=}}, the list must use named parameters, at least from that point. If you use named parameters, note that the first value is parameter 2 (e.g. |2=Your1stValue), because parameter 1 is the separator. If the separator contains an equals sign, {{=}} should also be used. Alternately, the separator can similarly be prefixed with "1=", but in that case it cannot contain newlines and spaces at the start and end. Also, if you use named parameters, you must not skip any numbers. The loop will terminate after the first absent numbered parameter. (Note that parameters can be blank but not absent; blank parameters are read as normal.)

Examples

Code Result
1{{for loop|, 1|00|01|02|03|04|05|06|07|08|09
|10|11|12|13|14|15|16|17|18|19
|20|21|22|23|24|25|26|27|28|29
|30|31|32|33|34|35|36|37|38|39
|40|41|42|43|44|45|46|47|48|49
|50|51|52|53|54|55|56|57|58|59
|60|61|62|63|64|65|66|67|68|69
|70|71|72|73|74|75|76|77|78|79
|80|81|82|83|84|85|86|87|88|89
|90|91|92|93|94|95|96|97|98|99
  |call=1x
}}
100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199

Note that the last part of the separator is used as a prefix; the first prefix needs to be put separately.


{{for loop|-|a|3||c|g|call=3x}} using Template:3x (backlinks · edit) gives

aaa-333--ccc-ggg

{{for loop|

|a|3||c|g|call=3x}} gives

aaa

333


ccc

ggg

{|class="wikitable sortable"
|-
!Test
|-
| {{for loop|
{{!}}-
{{!}} |a|b|c|d|e|call=3x}}
|}

gives:

Test
aaa
bbb
ccc
ddd
eee
{{for loop| |01|02|03|04|05|06|07|08|09|10|11|12|13|14|15|16|17|18|19
|20|21|22|23|24|25|26|27|28|29|30|31|32|33|34|35|36|37|38|39
|40|41|42|43|44|45|46|47|48|49|50|51|52|53|54|55|56|57|58|59
|60|61|62|63|64|65|66|67|68|69|70|71|72|73|74|75|76|77|78|79
|80|81|82|83|84|85|86|87|88|89|90|91|92|93|94|95|96|97|98|99
|100|101|102|103|104|105|106|107|108|109|110|111|112|113|114|115|116|117|118|119
|120|121|122|123|124|125|126|127|128|129|130|131|132|133|134|135|136|137|138|139
|140|141|142|143|144|145|146|147|148|149|150|151|152|153|154|call=1x}}

gives:

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154

begin->{{for loop|{{=}} |01|02|03|04|05|06|07|08|09|10
|11{{=}}{{=}}{{=}}|12|13|14|15|16|17|18|19|call=1x}}<-end

gives:

begin->01= 02= 03= 04= 05= 06= 07= 08= 09= 10= 11==== 12= 13= 14= 15= 16= 17= 18= 19<-end

Legacy code

This template is currently in its third incarnation. It is now uses the Lua code at Module:ForLoop. It was ported to Lua from ParserFunctions, and the old code is available at {{for loop/old}}. There was also a previous version with a named "sep" parameter to specify the separator value. The template was originally based on m:Template:For. The template name was changed because there was already a Template:For on Wikipedia.

The old versions were limited to 150 variable values and four fixed parameters. There are no such limits in the current version. Also, in the first version the "sep" parameter didn't allow whitespace in the separator value. This was fixed with the second version and was retained in the current version.

Substitution

The current Lua-based template supports substitution of the whole template call. To substitute everything, use {{subst:for loop}}.

The previous ParserFunctions-based template supported varying levels of substitution. If you wish to have fine-grained control over substitution, you need to use {{for loop/old}}. For successive levels of substitution use one or more or the following (the first, the first two, the first three, the first four, or all five).

  • "subst:" in front of "for loop/old" - substitute the call of {{for loop/old}}
  • substf=subst: - substitute the parser functions in {{for loop/old}}
  • substfa=subst: - substitute the call of {{ForLoop/aux}}, a helper subtemplate
  • substa=subst: - substitute the parser functions in {{ForLoop/aux}} (reduces the number of items from 150 to the actual number)
  • substc=subst: - substitute the calls of the user template

If at least the first four are applied, and the separator contains {{!}}, one can replace it with {{subst:!}} to substitute that too.

For full substitution Special:ExpandTemplates can also be used.

Converting legacy template invocations

If you need to convert a template invocation that was written for the original version of {{for loop}}, do the following:

  • replace pc1=X=Y with pc1n=X | pc1v=Y, etc.
  • use an unnamed parameter for the separator; if empty, just enter an extra "|"

No conversion is necessary for invocations written for the second version of the template, unless they use fine-grained substitution as mentioned in the section above. If you need fine-grained substitution you should use {{for loop/old}} instead of {{for loop}}. — Mr. Stradivarius ♪ talk ♪ 09:44, 19 July 2013 (UTC)

See also