Custom Blocks

[Robert Jacques]

On Thu, 12 Aug 2010 07:43:25 -0400, KennyTM~ <kennytm at gmail.com> wrote:

> On Aug 12, 10 10:25, Robert Jacques wrote:
>> On Wed, 11 Aug 2010 17:54:35 -0400, Tomek Sowiński <just at 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.