（返回值）

        return arg[n]     -- 返回第n个返回值，index从1开始

（传参）

function Window (options)    -- check mandatory options    if type(options.title) ~= "string" then    error("no title" )    elseif type(options.width) ~= "number" then    error("no width" )    elseif type(options.height) ~= "number" then    error("no height")    end    print(options.title)endw = Window {    x=0, y=0, width=300, height=200,    title = "-- > mark" , background= "blue",    border = true}

 

（闭包）

function newCounter()   local i = 0   return function () -- anonymous function     i = i + 1    return i   end end  c1 = newCounter() print(c1()) --> 1 print(c1()) --> 2

关键在于理解upvalue（external local variable ）， 这个变量是每个闭包独有的且是静态的！

 

（强大的迭代器） -- 一般难写易用

function allwords()    local file = io.open("test.lua", "r")    local line = file:read() -- current line    local pos = 1 -- current position in the line    return function () -- iterator function        while line do -- repeat while there are lines            local s, e = string.find(line, "%w+" , pos)            if s then -- found a word?                pos = e + 1 -- next position is after this word                return string.sub(line, s, e) -- return the word            else                line = file:read() -- word not found; try next line                pos = 1 -- restart from first position            end        end        file:close()        return nil -- no more lines: end of traversal    endendfor word in allwords() do    print(word)end