Re: [Vala] Confusing closure behavior

[Nor Jaidi Tuah <norjaidi tuah ubd edu bn>]

On Tue, 2019-04-09 at 08:25 +0200, Vivien Kraus wrote:
> Digging a little deeper, I have some more confusion.  This makes the
> for-loop and the foreach-loop behave differently.  What do you think
> of:
>
> // capturing the for variable should capture a copy if the variable
> is
> // local to the for loop
>
> public delegate void Thunk();
>
> int main() {
>       Thunk thunk = () => {};
>       for (int i = 0; i < 1; i++) {
>               thunk = () => {
>                       stderr.printf ("%d = 0, right?\n", i);
>               };
>       }
>       thunk ();
>       int[] indices = { 0 };
>       foreach (var i in indices) {
>               thunk = () => {
>                       stderr.printf ("%d = 0, right?\n", i);
>               };
>       }
>       thunk ();
>       return 0;
> }

I believe foreach pass the values inside the array.
e.g.,

   foreach (var i in indices) {
      i = 999;
   }

will not change indices[0] at all. A more strict language
will even forbid that "i = 999".


Nice day
Nor Jaidi Tuah




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