Revamping associative arrays

[BCS]

Hello Chris Nicholson-Sauls,

> Andrei Alexandrescu wrote:
> 
>> Associative arrays are today quite problematic because they don't
>> offer any true iteration. Furthermore, the .keys and .values
>> properties create new arrays, which is wasteful.
>> 
>> Another issue with associative arrays is that ++a[k] is hacked, which
>> reflects a grave language limitation. That needs to be replaced with
>> a true facility.
>> 
>> Any other issues with AAs that you want to see fixed, and ideas
>> guiding a redesign?
>> 
>> Thanks,
>> 
>> Andrei
>> 
> Idea: the .keys and .values properties, rather than creating arrays,
> could create iterable ranges with the smallest possible footprint,
> internally walking the tree structure.
> 

what will this do?

foreach(key; aa.keys)
   if(Test(key))
      aa.remove(key);