Module:Yesno/doc: Difference between revisions

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<noinclude>{{pp|small=yes}}

{{High-risk|over 15,600,000 pages, which is {{#expr:(1560000000/{{NUMBEROFPAGES:R}}) round 0}}% of all}}

</noinclude>{{used in system}}

{{Module rating|protected}}

{{cascade-protected template|page=module}}

This module provides a consistent interface for processing boolean or boolean-style string input. While Lua allows the <code>true</code> and <code>false</code> boolean values, wikicode templates can only express boolean values through strings such as "yes", "no", etc. This module processes these kinds of strings and turns them into boolean input for Lua to process. It also returns <code>nil</code> values as <code>nil</code>, to allow for distinctions between <code>nil</code> and <code>false</code>. The module also accepts other Lua structures as input, i.e. booleans, numbers, tables, and functions. If it is passed input that it does not recognise as boolean or <code>nil</code>, it is possible to specify a default value to return.

== Syntax ==

<sourcesyntaxhighlight lang="lua">yesno(value, default)</sourcesyntaxhighlight>

<code>value</code> is the value to be tested. Boolean input or boolean-style input (see below) always evaluates to either <code>true</code> or <code>false</code>, and <code>nil</code> always evaluates to <code>nil</code>. Other values evaluate to <code>default</code>.

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First, load the module. Note that it can only be loaded from other Lua modules, not from normal wiki pages. For normal wiki pages you can use {{tl|yesno}} instead.

<sourcesyntaxhighlight lang="lua">

local yesno = require('Module:Yesno')

</syntaxhighlight>

</source>

Some input values always return <code>true</code>, and some always return <code>false</code>. <code>nil</code> values always return <code>nil</code>.

<sourcesyntaxhighlight lang="lua">

-- These always return true:

yesno('yes')

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yesno('true')

yesno('t')

yesno('on')

yesno('1')

yesno(1)

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yesno('false')

yesno('f')

yesno('off')

yesno('0')

yesno(0)

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-- A nil value always returns nil:

yesno(nil)

yesno()

</source>

</syntaxhighlight>

String values are converted to lower case before they are matched:

<sourcesyntaxhighlight lang="lua">

-- These always return true:

yesno('Yes')

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yesno('N')

yesno('fALsE')

</syntaxhighlight>

</source>

===Undefined input ('foo')===

You can specify a default value if yesno receives input other than that listed above. If you don't supply a default, the module will return <code>nil</code> for these inputs.

<sourcesyntaxhighlight lang="lua">

-- These return nil:

yesno(nil)

yesno('foo')

yesno({})

yesno(5)

yesno('')

yesno(function() return 'This is a function.' end)

yesno(nil, true)

yesno(nil, 'bar')

-- These return true:

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yesno({}, true)

yesno(5, true)

yesno('', true) -- Returns true.

yesno(function() return 'This is a function.' end, true)

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yesno({}, 'bar')

yesno(5, 'bar')

yesno('', 'bar') -- Returns "bar".

yesno(function() return 'This is a function.' end, 'bar')

</syntaxhighlight>

</source>

Although the blankempty string usually evaluates to false in wikitext, it evaluates to true in Lua. This module prefers the Lua behaviour over the wikitext behaviour. If treating the blankempty string as false is important for your module, you will need to removeconvert blankempty argumentsstrings atto ana earliervalue stagethat ofevaluates processingto false before passing them to this module.<includeonly>{{#ifeq In the case of arguments received from wikitext, this can be done by using [[Module:{{SUBPAGENAME}}|sandbox||Arguments]].

===Handling nil results===

By definition:

<sourcesyntaxhighlight lang="lua">

yesno(''nil) -- Returns nil.

yesno('foo') -- Returns nil.

yesno(nil, true) -- Returns nil.

yesno(nil, false) -- Returns nil.

yesno('foo', true) -- Returns true.

</syntaxhighlight>

To get the binary <syntaxhighlight lang="lua" inline>true/false</syntaxhighlight>-only values, use code like:

<syntaxhighlight lang="lua">

myvariable = yesno(value or false) -- When value is nil, result is false.

myvariable = yesno(value or true) -- When value is nil, result is true. (XXX: when value is false, result is true...)

myvariable = yesno('foo') or false -- Unknown string returns nil, result is false.

myvariable = yesno('foo', true) or false -- Default value (here: true) applies, result is true.

</syntaxhighlight>

Better suggestions:

<syntaxhighlight lang="lua">

local myvariable = yesno(value)

if myvariable == nil then -- value is nil or an unrecognized string

myvariable = true

end

-- more efficient when value is nil, but more verbose

Note that the blank string also functions this way:

-- (note the default result has to be written twice)

<source lang="lua">

local myvariable

yesno('') -- Returns nil.

if value == nil then

yesno('', true) -- Returns true.

myvariable = true

yesno('', 'bar') -- Returns "bar".

else

</source>

myvariable = yesno(value, true)

end

</syntaxhighlight><!--

--><includeonly>{{sandbox other||

Although the blank string usually evaluates to false in wikitext, it evaluates to true in Lua. This module prefers the Lua behaviour over the wikitext behaviour. If treating the blank string as false is important for your module, you will need to remove blank arguments at an earlier stage of processing.<includeonly>{{#ifeq:{{SUBPAGENAME}}|sandbox||

[[Category:Lua metamodules]]

}}</includeonly>

<noinclude>

[[Category:Module documentation pages]]

</noinclude>