Lua 中的可变长函数

Lua中的可变长函数的参数用 ... 来表示 ( 3个 . )

在函数内部有一个特殊的内置变量   arg

 

其格式如下

arg =

{

    1,

    "Hello",

    true,

    n = 3

}

 

 

-- function  makeVarStr(...) to see print_Table.lua

function printMultiArg(...)
    print("... = " .. makeVarStr(arg))
end


function my_print1(fmt, ... )
    print("=================== Begin my_print1 ===================")
    print("fmt = " .. makeVarStr(fmt))


    print("... = " .. makeVarStr(arg))
    print("=================== End my_print1 ===================\n")
end

function my_print2(fmt, ... )
    print("=================== Begin my_print2 ===================")
    print("fmt = " .. makeVarStr(fmt))

    printMultiArg(arg)
    print("=================== End my_print2 ===================\n")
end

function my_print3(fmt, ... )
    print("=================== Begin my_print3 ===================")
    print("fmt = " .. makeVarStr(fmt))

    printMultiArg(...)
    print("=================== End my_print3 ===================\n")
end



a =1
b = "Hello"
c = true
my_print1("a = ??? , b = ??? , c= ??? ",a,b,c)
my_print2("a = ??? , b = ??? , c= ??? ",a,b,c)
my_print3("a = ??? , b = ??? , c= ??? ",a,b,c)

--[[
=================== Begin my_print1 ===================
fmt = "a = ??? , b = ??? , c= ??? "
... = 
{
   [1] = 1,
   [2] = "Hello",
   [3] = true,
   "n" = 3,
}
=================== End my_print1 ===================

=================== Begin my_print2 ===================
fmt = "a = ??? , b = ??? , c= ??? "
... = 
{
   [1] = 
   {
      [1] = 1,
      [2] = "Hello",
      [3] = true,
      "n" = 3,
   },
   "n" = 1,
}
=================== End my_print2 ===================

=================== Begin my_print3 ===================
fmt = "a = ??? , b = ??? , c= ??? "
... = 
{
   [1] = 1,
   [2] = "Hello",
   [3] = true,
   "n" = 3,
}
=================== End my_print3 ===================


]]

 

##############################

Nice Version 1

Use select(n, ...) expression

##############################

 

--[[
//////////////////////////////////////////////////////////////////////////////////////////////////////             
//  Lua Interpret will assignment 
//    The command line arguments as the internal build-in argument named "arg" 
//       instead of "..." in the function argument list
//
//        Variadic Arguments
//
//
//////////////////////////////////////////////////////////////////////////////////////////////////////             
--]]

function printAll(fmt, ...)
    print("---------- Begin printAll() ----------\n")
    print("fmt = " .. fmt)
    print("arg = " , ... )
    print()

    --
    -- yield the argument list's  Count
    --
    print("# ... = ", select("#", ...) )

    print("******************************")
    for i=1,select("#", ...) do
        -- Here           : (              )  is a must 
        -- ********************************************************************************************************************
        --                  (              ) ==>  force "select(...)" function return only one argument rathan than multiple arguments
        -- ********************************************************************************************************************
        print("  ",i," = ", (select(i, ...)) )
    end
    print("******************************\n")

    print("---------- End printAll() ----------")
end


printAll("Hello-World : ", "a1", "b2", "c3" , 3.14, true, false, nil , "end"); 

---------- Begin printAll() ----------

 

fmt = Hello-World :

arg =    a1   b2   c3   3.14   true   false   nil    end

 

# ... = 8

******************************

　　1 = a1

　　2 = b2

　　3 = c3

　　4 = 3.14

　　5 = true

　　6 = false

　　7 = nil

　　8 = end

******************************

 

---------- End printAll() ----------

 

 

####################################

Nice Version 2

Use 'arg' internal varible

instead of '...' <= Variadic arguments

###################################

 

print("--------------------------------------------------")
print("outside arg = ",arg)
print("outside arg.n = ",arg.n)
print("--------------------------------------------------\n")


local newgt = { 
    printAll = function(fmt, ...)
        print("fmt = ",fmt)
        print("inner   arg = ", arg)
        print("inner   arg.n = ", arg.n)

        for i,v in pairs(arg) do
            print("\t",i,v)
        end
        return "Done"
    end

}
setmetatable(newgt, { __index = _G })

-- setfenv(...) is avaliable only in lua5.1
setfenv(1, newgt)



print("                                   [1]   [2]  [3]   [4]    [5]  [6]  [7]")
print("Calling " .. [[printAll("format : %d%c", "a1", "b2", "c3", 3.14, true, nil ,false)]])
print( printAll("format : %d%c", "a1", "b2", "c3", 3.14, true, nil ,false) )

 

--------------------------------------------------

outside arg = table: 00B302A0

outside arg.n = nil

--------------------------------------------------

 

                                                    [1]     [2]     [3]    [4]    [5]    [6]    [7]

Calling printAll("format : %d%c", "a1", "b2", "c3", 3.14, true, nil ,false)

fmt = format : %d%c

inner arg = table: 00B30138

inner arg.n = 7

　　1 a1

　　2 b2

　　3 c3

　　4 3.14

　　5 true

　　7 false

　　n 7

Done