associative arrays: iteration is finally here

[Andrei Alexandrescu]

Walter has magically converted his work on T[new] into work on making 
associative arrays true templates defined in druntime and not considered 
very special by the compiler.

This is very exciting because it opens up or simplifies a number of 
possibilities. One is that of implementing true iteration. I actually 
managed to implement last night something that allows you to do:

int[int] aa = [ 1:1 ];
auto iter = aa.each;
writeln(iter.front.key);
writeln(iter.front.value);

Two other iterations are possible: by key and by value (in those cases 
iter.front just returns a key or a value).

One question is, what names should these bear? I am thinking of makign 
opSlice() a universal method of getting the "all" iterator, a default 
that every container must implement.

For AAs, there would be a "iterate keys" and "iterate values" properties 
or functions. How should they be called?


Thanks,

Andrei