Re: [proposal] A statement that can return value (and can used in expr)

[Xavier Wang <weasley.wx@...>]

2011/12/14 Luiz Henrique de Figueiredo <lhf@tecgraf.puc-rio.br>:
>> local a = (function(a, b) print "a statement" return a + b end)(10, 20) + 30
>
> Lua 5.1 will create a new closure every time this statement is execute.
> Lua 5.2 will not: it will resuse the closure.
>
> Try the code below in each version:
>
> for i=1,3 do
>        local f = function(a, b) print "a statement" return a + b end
>        local a = f(10, 20) + 30    + i
>        print(f,a)
> end
>
Thank you for fast reply :-)

the promise only apply when you don't use upvalue, try this:

for i = 1, 3 do
   local c = 10
   local function f(a, b) print "a statement" return a + b + c end
   local a = f(10 + 20) + 30
   print(f, a)
end

In this case, three closure will created, but they are needn't create
twice (they only execute once).

So, Is there any optimizing to make sure if a function only execute
once, there are needn't create once? or a new syntax form can hold
this situation?

thanks Luiz :-)