spir wrote:
> On Thu, 02 Dec 2010 08:54:43 -0800
> Ali Çehreli <[email protected]> wrote:
>
>> bearophile wrote:
>> > Pelle M.:
>> >
>> >> It doesn't exist for performance reasons, I think.
>> >
>> > It's not a matter of performance. Walter thinks that "in" on
>> > AAs searches on keys. And the "keys" of a dynamic array are its
>> > indices. And searching for indices in a dynamic array is not so
>> > useful. Therefore no "in" for dynamic/static arrays. I think
>> > this line of thought is not practical, and Python gets this
>> > better.
>>
>> I think Walter's is a good point. If 'in' searches among keys for AAs;
>> for arrays, it would be implemented trivially as
>>
>> (index >= 0) && (index < array_length)
>
> That's not the point...
>
>> I think that expression allows for negative index values too. And
yes, I
>> had to check before posting as I can't be sure about the integer
>> promotion rules. :)
>>
>> If 'in' were to search among the values of arrays, then it wouldn't
have
>> the same meaning with AAs.
>
> Yes-no. In an ordered set (read: many uses of arrays),
I disagree with that. Arrays are for consecutive elements, usually
unordered. The index is their position in the collection.
> elements
> conceptually are their own keys. We must have a simple way to
> express membership test -- even if possibly costly for large
> arrays. Else, we need a builtin Set type to do the job. (I have
> one prototype in stock, if interesting for Phobos).
Agreed but that's a completely different data structure. Sets cannot
satisfy the O(1) operations of arrays.
I was responding related to D's arrays, which are not sets.
Ali
