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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>.

 

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.

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

-- These always return true:

-- These always return false:

-- A nil value always returns nil:

 

 

-- These always return true:

-- These always return false:

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.

-- These return nil:

-- These return true:

-- These return "bar":

 

 

<syntaxhighlight lang="lua">

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:

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 lang="lua">

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

    myvariable = true

 

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

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

</syntaxhighlight><!--

 

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