Help:Parameter default

Limitation

In the case of multiple default parts, only the first applies: [a|b|c|d] is equivalent with [a|b]. The default part can only contain "|" as part of full template, parameter or link syntax within it, and within nowiki-tags. Note that "|" can be avoided in table syntax by applying HTML coding (element "<table>").

The expression for the parameter name can also contain "|", as part of full template or parameter syntax within it.

Examples, using Template:x3 containing "<noinclude>{{Please leave this line alone (template sandbox heading)}}<!-- * Welcome to the template sandbox! * * Please leave this part alone * * The page is cleared regularly * * Feel free to try your editing skills below * ■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■--></noinclude>"
and Template:t2 containing "[[w:List of people by name: {{{1}}}{{{2}}}|{{{1}}}{{{2}}}]]<noinclude>[[Category:Help:Templates templates]]</noinclude>":

• {{{a|b|c|d}}} gives b
• {{{a|{{x3|b}}}}} gives
• {{{a|{{{b|c}}}}}} gives c
• {{{a|[[b|c]]}}} gives c
• {{{{{x3|a}}|b}}} gives b - parameter aaa is undefined
• {{{{{{a|b}}}|c}}} gives c - parameter b is undefined

• {{{a|<nowiki>b|c</nowiki>}}} gives b|c - works fine for rendering text, but is not suitable for putting parameters b and c in a template call (there is no function for removing nowiki tags):

  {{t2|{{{a|<nowiki>b|c</nowiki>}}}}} gives [[w:List of people by name: b|c{{{2}}}|b|c{{{2}}}]]

Repetition

A "for-loop" is achieved using

m:Template:fors (backlinks edit), containing:

---

{{fors/aux
  |v@=
  |c={{{call}}}
  |pv={{{pv|1}}}
  |s={{{sep|}}}
  |pc1={{{pc1|=}}}
  |pc2={{{pc2|=}}}
  |pc3={{{pc3|=}}}
  |pc4={{{pc4|=}}}|
1={{{1|@}}}|2={{{2|@}}}|3={{{3|@}}}
}}

---

with m:Template:fors/aux (backlinks edit), containing:

---

{{{v{{{1}}}|{{{{{c}}}|{{{pc1}}}|{{{pc2}}}|{{{pc3}}}|{{{pc4}}}|{{{pv}}}={{{1}}}}}}}}
{{{v{{{2}}}|{{{s}}}{{{{{c}}}|{{{pc1}}}|{{{pc2}}}|{{{pc3}}}|{{{pc4}}}|{{{pv}}}={{{2}}}}}}}}
{{{v{{{3}}}|{{{s}}}{{{{{c}}}|{{{pc1}}}|{{{pc2}}}|{{{pc3}}}|{{{pc4}}}|{{{pv}}}={{{3}}}}}}}}

---

In short form the latter consists of components

[ v[i] | [s] {{[c]|[pc1]|[pc2]|[pc3]|[pc4]|[pv]=[i]}} ] (i = 1, 2, 3, for i = 1 without [s])

or in terms of the parameters of the first template:

[v[i|@] | [sep|] {{[call]|[pc1|]|[pc2|]|[pc3|]|[pc4|]|[pv|1]=[i]}} ]

This is indeed of the above-mentioned form [a[b|c]|f([b])], with a=v, b=i, c=@, and

f(x) = [sep|] {{[call]|[pc1|]|[pc2|]|[pc3|]|[pc4|]|[pv|1]=x}}

The assumptions mentioned above apply for d equal to null, and provided that no [i] is equal to "@".

Variations

Since v@=null we can also take make the concatenation the outer operation: [v[i|@] | [sep|]] [v[i|@] | {{[call]|[pc1|]|[pc2|]|[pc3|]|[pc4|]|[pv|1]=[i]}} ]