Module:Yesno

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]

   -- According to the template docs, the input should be considered nil
   -- only when no params were provided. If any params at all were present,
   -- the value must be considered blank. A bit weird, if you ask me.
   if (val == nil and not any) or val == '¬' then
       return retvals['¬']
   end

   val = (val or ):lower()          -- Coerce to blank if nil; make lowercase.
   val = val:match'^%s*(.*%S)' or   -- Trim whitespace.

   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

return p