associative arrays: iteration is finally here

[Andrei Alexandrescu]

Denis Koroskin wrote:
> On Wed, 28 Oct 2009 23:18:08 +0300, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> wrote:
> 
>>> I'd also like you to add a few things in an AA interface.
>>>  First, opIn should not return a pointer to Value, but a pointer to a 
>>> pair of Key and Value, if possible (i.e. if this change won't 
>>> sacrifice performance).
>>
>> I'm coy about adding that because it forces the implementation to hold 
>> keys and values next to each other. I think that was a minor mistake 
>> of STL - there's too much exposure of layout details.
>>
> 
> It doesn't have to be the case: key and value are both properties (i.e. 
> methods), and they doesn't have to be located next to each other.

I see. So you want a pointer to an elaborate type featuring a key and a 
value.

>>> Second, AA.remove method should accept result of opIn operation to 
>>> avoid an additional lookup for removal:
>>>  if (auto value = key in aa) {
>>>     aa.remove(key); // an unnecessary lookup
>>> }
>>
>> I'll make aa.remove(key) always work and return a bool that tells you 
>> whether there was a mapping or not.
>>
> 
> Err... How does it solve the double lookup problem?

Your test looks something up and then removes it.


Andrei