Template:For loop
 | This template is used on approximately 802,000 pages, or roughly 1% of all pages. To avoid major disruption and server load, any changes should be tested in the template's /sandbox or /testcases subpages, or in your own user subpage. The tested changes can be added to this page in a single edit. Consider discussing changes on the talk page before implementing them. |
 | This template uses Lua: |
This template implements a for loop or a foreach loop.
This template calls a user-specified template (the "called template") multiple times: once for each value in either 1) an iterated sequence or 2) an explicit list. Each value in the sequence or list is passed to the same specified parameter of the called template (the "variable parameter"). Optionally, pre- and postfixes can be attached to the passed values.
In addition to the specified variable parameter, other parameters of the called template ("static parameters") can be given a value which is the same in each iteration.
Usage
| Group | Parameter | Meaning | Default value |
|---|---|---|---|
| Mandatory | 1 (unnamed) | separator to output between calls (may be blank; whitespace is preserved) | |
| call | template to call | ||
| pv | name (or number) of the variable parameter of the called template | 1 | |
| Option 1: iterated sequence |
start | first numeric value to pass to variable parameter | 1 |
| stop | maximum numeric value for variable parameter | ||
| by | iteration step size between values passed to variable parameter | 1 | |
| Option 2: explicit values |
(unnamed parameters) | explicit values, given as separate parameters (whitespace is stripped) | |
| skipBlanks | set to "true" to skip empty parameter values | false | |
| Other optional parameters |
pc[N]n | name (or number) of the Nth static parameter of the called template | |
| pc[N]v | value for the Nth static parameter of the called template | ||
| prefix | static prefix prepended to each value passed to the variable parameter | ||
| postfix | static postfix appended to each value passed to the variable parameter | ||
| substall | set to "false" to not substitute the called template when {{for loop}} is substituted | true |
Either option 1 (iteration parameters) or option 2 (an explicit list of values) may be used, but not both.
The first unnamed parameter, prior to any explicit values, is a separator. The separator is a string that is output between calls to the template named in |call=. It is not output after the last call.
Caution
- The separator can be prefixed with "1=", but in that case it cannot contain newlines and spaces at the start and end.
- If any parameter value contains an equals sign, use
{{=}}(see Template Usage hints and workarounds). - If you use numbered parameters, note that the first value is parameter 2 (e.g.
|2=Your1stValue), because parameter 1 is the separator. - If you use numbered parameters, you must not skip any numbers. The loop will terminate after the first absent numbered parameter. (Parameters can be blank, but not absent.)
Substitution
The current Lua-based template supports substitution. If |substall=no is not specified, then substituting the template will substitute everything, including the call to the template passed in |call=. If it is specified, then the template substitutes into a sequence of calls to the template specified.
Example: {{subst:for loop|sep|01|02|03|04|05|06|07|call=1x}} -> 01sep 02sep 03sep 04sep 05sep 06sep 07, {{subst:for loop|sep|01|02|03|04|05|06|07|substall=no}} -> {{1x|01}}sep {{1x|02}}sep {{1x|03}}sep {{1x|04}}sep {{1x|05}}sep {{1x|06}}sep {{1x|07}}
For full substitution Special:ExpandTemplates can also be used.
Examples
| Form | Code | Explanation | Result |
|---|---|---|---|
| Iterator |
{{for loop|&
|call = spanbox
|pv = font size
|start=10
|stop=52
|by=8
|postfix = px
|pc1n = 1
|pc1v = A
|pc2n = background
|pc2v = yellow
}}
|
Call the template "spanbox" with values:
Separating outputs with "&" |
A &A &A &A &A &A
|
| Explicit values | {{for loop|, |call=2x
|prefix=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 the template {{2x}} (which just repeats its input twice) with values "1[NN]", where NN = "00" through "99" (given explicitly), separating the outputs with the string ", " | 100100, 101101, 102102, 103103, 104104, 105105, 106106, 107107, 108108, 109109, 110110, 111111, 112112, 113113, 114114, 115115, 116116, 117117, 118118, 119119, 120120, 121121, 122122, 123123, 124124, 125125, 126126, 127127, 128128, 129129, 130130, 131131, 132132, 133133, 134134, 135135, 136136, 137137, 138138, 139139, 140140, 141141, 142142, 143143, 144144, 145145, 146146, 147147, 148148, 149149, 150150, 151151, 152152, 153153, 154154, 155155, 156156, 157157, 158158, 159159, 160160, 161161, 162162, 163163, 164164, 165165, 166166, 167167, 168168, 169169, 170170, 171171, 172172, 173173, 174174, 175175, 176176, 177177, 178178, 179179, 180180, 181181, 182182, 183183, 184184, 185185, 186186, 187187, 188188, 189189, 190190, 191191, 192192, 193193, 194194, 195195, 196196, 197197, 198198, 199199 |
| Explicit values | {{for loop||call=tsh|skipBlanks=true|{{#switch:{{ROOTPAGENAME}}
|Namespace links=ln
|Article links=la
}}}} <!--Don't show {{tsh}} for |Lafd=lafd -->
|
{{for loop}} is useful for omitting a template call with one parameter being an inline expression that can be empty. It avoids repeating the parameter that the usual {{{1|}}} {{#if:{{{1|}}}|{{example|{{{1}}}}}}} does.
|
({{for loop}} helped avoid the error message) |
Other examples with explicit values
{{for loop|-|a|3||c|g|call=3x}}
aaa-333-ccc-ggg
{{for loop|
|a|3||c|g|call=3x}}
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
Notes about legacy code
This template is currently in its third incarnation. It now uses the Lua code at Module:For loop. It was ported to Lua from ParserFunctions. There was also a previous version with a named "sep" parameter to specify the separator value. The template was originally based on Template:For on meta. 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.