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]

    -- First deal with the case if val is nil, then deal with other cases.
    if val == nil 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