Re: Custom Blocks

[Robert Jacques]

On Thu, 12 Aug 2010 07:43:25 -0400, KennyTM~ <kenn...@gmail.com> wrote:
On Aug 12, 10 10:25, Robert Jacques wrote:
On Wed, 11 Aug 2010 17:54:35 -0400, Tomek Sowiński <j...@ask.me> wrote:

Robert Jacques napisał:

I was thinking something like this:

void fun(int x, int y, int z, delegate void(int, int, int) dg)

fun(x, y, z, a, b, c) { body }

|
V

fun(x, y, z, (a, b, c) { body });

Mixing function args with delegate args makes me think of foreach:

fun(x, y, z, (a, b, c) { body }); <=> fun(a, b, c; x, y, z) { body }

All great, but if there's no remedy for the return WTF, I'd leave this
(nice) feature in the drawer.

void foo() {
fun(a, b, c; x, y, z) {
return; // who returns?
}
}


Tomek

Fun does. This is the same as function/delegate literals today.
Of course, putting a return statement inside a foreach block is probably
a buggy edge case right now; sometimes it causes the parent scope to
return and sometimes it doesn't compile.

This is an unacceptable buggy edge case. Consider the already-working  
code

    int find_three(int[] arr) {
      foreach (i, x; arr) {
        if (x == 3)
          return i;
      }
      return -1;
    }

If I replace the foreach with a custom block e.g.

    int find_three_retro(int[] arr) {
      foreach_retro (i, x; arr) {
        if (x == 3)
          return i;
      }
      return -1;
    }

then suddenly the function doesn't work anymore. It's better not to  
provide a feature inconsistent with other parts of the language.

Code that exploits a bug in the implementation isn't "working" in any  
sense of the word. One of the points I was making is that return  
statements inside a foreach do different things depending on what you're  
foreaching over. So this feature would be adding consistency, not removing  
it.