Custom Blocks

[KennyTM~]

On Aug 12, 10 23:42, Robert Jacques wrote:
> 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.



void locate_three_or_five(int[] arr) {
    int res = -1;
    foreach (i, x; arr) {
       if_is_one_of(x, [3, 5]) {
          res = i;
          break;     // now what?
       }
    }
    writeln("found 3 or 5 at ", res);
}