Module:Yesno

Yesno is a function that converts various "affirmative" and "negative" inputs in modules into booleans; "yes", "Y", 1 "true", "t" and "on" are all converted into a true boolean, and "no", "N", 0, "false", "f" and "off" are converted to a false boolean. This is for consistent treatment of boolean-like wikitext input.

---

-- 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