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{{ | {{doc sub}} | ||
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. | 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. | ||
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===Handling nil results=== | ===Handling nil results=== | ||
By definition | By definition: | ||
<syntaxhighlight lang="lua"> | |||
yesno(nil) -- Returns nil. | yesno(nil) -- Returns nil. | ||
yesno('foo') -- Returns nil. | yesno('foo') -- Returns nil. | ||
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<syntaxhighlight lang="lua"> | <syntaxhighlight lang="lua"> | ||
myvariable = yesno(value or false) -- When value is nil, result is false. | myvariable = yesno(value or false) -- When value is nil, result is false. | ||
myvariable = yesno(value or true) -- When value is nil, result is true. | 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') or false -- Unknown string returns nil, result is false. | ||
myvariable = yesno('foo', true) or false -- Default value (here: true) applies, result is true. | 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><!-- | </syntaxhighlight><!-- | ||
--><includeonly>{{sandbox other|| | --><includeonly>{{sandbox other|| | ||
[[Category:Modules]] | |||
[[Category:Lua metamodules]] | [[Category:Lua metamodules]] | ||
}}</includeonly> | }}</includeonly> | ||
<noinclude> | |||
[[Category:Module documents]] | |||
</noinclude> | |||