Super-dee-duper D features

[Bill Baxter]

kris wrote:
> Bill Baxter wrote:
>> kris wrote:
>>
>>> kris wrote:
>>>
>>>> Bill Baxter wrote:
>>>>
>>>>> Frits van Bommel wrote:
>>>>>
>>>>>> By the way, would the new loop syntax allow more than two 
>>>>>> collections to be simultaneously iterated?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Whoa!  I certainly hope so.  It hadn't even occurred to me that 
>>>>> Andrei might mean this syntax can only be used for just two 
>>>>> collections.  If that's the case then ... ick.
>>>>>
>>>>> --bb
>>>>
>>>>
>>>>
>>>> InterleavedIterator does multiple collections via using multiple 
>>>> instances of InterleavedIterator. It's simple to use, and only needs 
>>>> to be written once. Would be better to implement some basic iterator 
>>>> needs than to introduce some tricky new syntax?
>>>>
>>>> - Kris
>>>
>>>
>>>
>>> Should have given an example. Simple case with 2 entities:
>>>
>>> auto two = InterleavedInterator (x, y);
>>> foreach (x; two) ...
>>>
>>> more than 2:
>>>
>>> auto three = InterleavedInterator (two, z);
>>> foreach (x; three) ...
>>
>>
>> Should have also mentioned where one can find this mythical 
>> InterleavedIterator.
>>
>> --bb
> 
> There is no 'standard' one at this time that I know of (judging by the 
> discussion on it a while back). However, Tango does have this beastie in 
> the collections package. The point is, coming up with a lightweight core 
> Iterator approach would likely provide a simpler and more dependable 
> solution.

Ok that wasn't clear to me.  It sounded like you were talking about code 
I could type in today and have it work given suitable (but not 
specified) imports.

> in the above example, x, y, and z are all iterators themselves. If D had 
> a core notion of Iterator, that's what those would be. For instance, D 
> iterators might map to a delegate (which is what the body of a foreach 
> actually is).

Yeh, basically it's the same as the Python izip that mentioned.  That's 
python's name for InterleavedIterator.

I think the issue with D right now is that the 'x' returned by a 
hypothetical InterleavedIterator would ideally be a tuple.  And you 
would access the elements with x[0],x[1],x[2] (int the 'three' case 
above).  Or you could do  foreach(x,y,z; three) and have it unpacked for 
you.

I think it would be great if this kind of stuff worked.  I'm much less 
excited about a built-in syntax that _only_ knows how to do that one trick.

--bb