Module:Yesno
Lua error in Module:High-use at line 137: attempt to call upvalue 'yesno' (a table value).
Lua error in Module:Message_box at line 165: attempt to call upvalue 'yesno' (a table value).
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')
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 nil
for these inputs.
-- These return nil: yesno('foo') yesno({}) yesno(5) yesno(function() return 'This is a function.' end) yesno(nil, true) yesno(nil, 'bar') -- 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 empty string also functions this way:
yesno('') -- Returns nil. yesno('', true) -- Returns true. yesno('', 'bar') -- Returns "bar".
Although the empty 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 empty string as false is important for your module, you will need to convert empty strings to a value that evaluates to false before passing them to this module. In the case of arguments received from wikitext, this can be done by using Module:Arguments.
Handling nil results
By definition
yesno(nil) -- Returns nil.
yesno('foo') -- Returns nil. yesno(nil, true) -- Returns nil. yesno(nil, false) -- Returns nil.
yesno('foo', true) -- Returns true.To get the binary true/false
-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. 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.
local p = {} function p.yesno(frame) -- defaults local retvals = { yes = "yes", no = "", ["¬"] = "" } -- Allow arguments to override defaults. -- 'any' tracks the presence of any arguments at all. local args = frame.args local any = false for k,v in pairs(args) do any = true retvals[k] = v end -- If there are no arguments, try and get them from the parent frame. if any == false then local pframe = frame:getParent() args = pframe.args for k,v in pairs(args) do any = true retvals[k] = v end end val = args[1] -- First deal with the case if val is nil or "¬", then deal with other cases. if val == nil or val == '¬' then return retvals['¬'] end val = val:lower() -- Coerce to blank if nil; make lowercase. val = val:match'^%s*(.*%S)' or '' -- Trim whitespace. if val == '' then return 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 return p