在 Lua 中定义函数

Question

I read that we can declare a function in Lua with two different syntax:

function pr()
    print("I'm function pr()")
end

printt = function()
    print("I'm function printt()")
end

pr()
printt()

Though the functions seem to work exactly the same way when they're called I want to know if there's a difference between their implementation at lower level. Does the interpretor treats them exactly the same or do they differ in terms of speed, implementation, or in any way?

Answer 1

There's no real difference between the two. The first one is just a syntactic sugar to the second form.

From the reference manual Function Definitions :

The syntax for function definition is

 functiondef ::= function funcbody funcbody ::= '(' [parlist] ')' block end

The following syntactic sugar simplifies function definitions:

 stat ::= function funcname funcbody stat ::= local function Name funcbody funcname ::= Name {'.' Name} [':' Name]

The statement

 function f () body end

translates to

 f = function () body end