Module:Yesno/doc: Difference between revisions

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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 ==

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

<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>.

== Usage ==

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===Handling nil results===

By definition:

:<syntaxhighlight lang="lua">

yesno(nil) -- Returns nil.

yesno('foo') -- Returns nil.

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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 the default result has to be written twice)

local myvariable

if value == nil then

myvariable = true

else

myvariable = yesno(value, true)

end

</syntaxhighlight><!--

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[[Category:Lua metamodules]]

}}</includeonly>

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[[Category:Module documentation pages]]

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