Lua

[lollospadalaser]

i have an easy question, i don't understand why this works:

local fact
  fact= function (n)
  if n == 0 then return 1
  else return n*fact(n-1)
  end
end

print(fact(4))

and this one not:

local fact = function (n)
  if n == 0 then return 1
  else return n*fact(n-1)
  end
end

print(fact(4))

i don't understand the difference, why declaring it first make it works? If i remove the local they both works as expected

 

[BorkedSystem32]

Hello there, @lollospadalaser.

I've found the example from the PIL manual you're talking about here.

I've found this statement within it that may possibly explain why the first works and the second doesn't:

When Lua compiles the call fact(n-1), in the function body, the local fact is not yet defined. Therefore, that expression calls a global fact, not the local one. To solve that problem, we must first define the local variable and then define the function: ...

To sum up: when you make the function call, fact(n-1) is called in the function body, but it can't find the local fact because the interpreter does not believe it's been defined. So, the interpreter attempts to find a global fact and the program encounters a bug because there is no global fact and we get the following error: lua: file.lua:5: global 'fact' is not callable (a nil value):

I hope that explains it. If you'd like to read further into it, use the link I gave you above as that will better explain it alongside the examples.

 

[lollospadalaser]

ok, thanks, i understand now.