Difference between revisions of "Module:Yesno"

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local p = {}
+
-- Function allowing for consistent treatment of boolean-like wikitext input.
+
-- It works similarly to the template {{yesno}}.
function p.yesno( frame )
+
 
+
return function (val, default)
    -- defaults
+
-- If your wiki uses non-ascii characters for any of "yes", "no", etc., you
    local retvals = {
+
-- should replace "val:lower()" with "mw.ustring.lower(val)" in the
        yes  = "yes",
+
-- following line.
        no   = "",
+
val = type(val) == 'string' and val:lower() or val
        ["¬"] = ""
+
if val == nil then
    }
+
return nil
+
elseif val == true
    -- Allow arguments to override defaults.
+
or val == 'yes'
    -- 'any' tracks the presence of any arguments at all.
+
or val == 'y'
    local any = false
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or val == 'true'
    for k,v in pairs( frame.args ) do
+
or val == 't'
        any = true
+
or val == 'on'
        retvals[k] = v
+
or tonumber(val) == 1
    end
+
then
+
return true
    val = frame.args[1]
+
elseif val == false
+
or val == 'no'
    -- According to the template docs, the input should be considered nil
+
or val == 'n'
    -- only when no params were provided. If any params at all were present,
+
or val == 'false'
    -- the value must be considered blank. A bit weird, if you ask me.
+
or val == 'f'
    if (val == nil and not any) or val == '¬' then
+
or val == 'off'
        return retvals['¬']
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or tonumber(val) == 0
    end
+
then
+
return false
    val = (val or ''):lower()          -- Coerce to blank if nil; make lowercase.
+
else
    val = val:match'^%s*(.*%S)' or '' -- Trim whitespace.
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return default
+
end
    if val == '' then
 
        return retvals['blank'] ~= nil and retvals['blank'] or retvals['no']
 
    elseif val == 'n' or val == 'no' or val == '0' then
 
        return retvals['no']
 
    elseif val == 'y' or val == 'yes' or val == '1' or retvals['def'] == nil then
 
        return retvals['yes']
 
    else
 
        return retvals['def']
 
    end
 
 
end
 
end
 
return p
 

Latest revision as of 18:47, 2 November 2019

This module provides a consistent interface for processing boolean or boolean-style string input. While Lua allows the true and false 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 nil values as nil, to allow for distinctions between nil and false. 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 nil, it is possible to specify a default value to return.

Syntax

yesno(value, default)

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

Usage

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 {{yesno}} instead.

local yesno = require('Module:Yesno')

Some input values always return true, and some always return false. nil values always return nil.

-- These always return true:
yesno('yes')
yesno('y')
yesno('true')
yesno('t')
yesno('1')
yesno(1)
yesno(true)

-- These always return false:
yesno('no')
yesno('n')
yesno('false')
yesno('f')
yesno('0')
yesno(0)
yesno(false)

-- A nil value always returns nil:
yesno(nil)

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

-- These always return true:
yesno('Yes')
yesno('YES')
yesno('yEs')
yesno('Y')
yesno('tRuE')

-- These always return false:
yesno('No')
yesno('NO')
yesno('nO')
yesno('N')
yesno('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 nil for these inputs.

-- These return nil:
yesno('foo')
yesno({})
yesno(5)
yesno(function() return 'This is a function.' end)

-- These return true:
yesno('foo', true)
yesno({}, true)
yesno(5, true)
yesno(function() return 'This is a function.' end, true)

-- These return "bar":
yesno('foo', 'bar')
yesno({}, 'bar')
yesno(5, 'bar')
yesno(function() return 'This is a function.' end, 'bar')

Note that the blank string also functions this way:

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

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.


-- Function allowing for consistent treatment of boolean-like wikitext input.
-- It works similarly to the template {{yesno}}.

return function (val, default)
	-- If your wiki uses non-ascii characters for any of "yes", "no", etc., you
	-- should replace "val:lower()" with "mw.ustring.lower(val)" in the
	-- following line.
	val = type(val) == 'string' and val:lower() or val
	if val == nil then
		return nil
	elseif val == true 
		or val == 'yes'
		or val == 'y'
		or val == 'true'
		or val == 't'
		or val == 'on'
		or tonumber(val) == 1
	then
		return true
	elseif val == false
		or val == 'no'
		or val == 'n'
		or val == 'false'
		or val == 'f'
		or val == 'off'
		or tonumber(val) == 0
	then
		return false
	else
		return default
	end
end