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.
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
.
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 (eg.
Yes
) always return
true
, and some (eg.
No
) always return
false
.
nil
values always return
nil
.
-- These always return true:
yesno
(
'yes'
)
yesno
(
'y'
)
yesno
(
'true'
)
yesno
(
'1'
)
yesno
(
1
)
yesno
(
true
)
-- These always return false:
yesno
(
'no'
)
yesno
(
'n'
)
yesno
(
'false'
)
yesno
(
'0'
)
yesno
(
0
)
yesno
(
false
)
-- Nil values always return 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'
)
-- Because string "foo" doesn't a truth value, so the yesno function return nil.
-- "Si" in Breton language or "いいえ" in Japanese will return nil.
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.
Code
-- 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