Iterators for D

[Bill Baxter]

Walter Bright wrote:
> Tom S wrote:
>> Walter Bright wrote:
>>> foreach loops will not be able to have a 'key' parameter.
>> What's the particular reason for that restriction ?
> 
> With an iterator, what is the key?

It could just be the count.  Say I'm trying to linearize a non-linear 
datastructure into a pre-existing array:


    foreach(int i, val v; hierarchical_thing.iterator())
    {
       linearized[i] = val;
    }

Also having the count there would make it easier to do something like 
iterating lock step in funky ways over different objects:

    foreach(int i, val v; thing.randomized_iterator()) {
       other_thing[i] = val;
    }

Obviously you could count things yourself if you had to.
But I find for instance in Python that I use 'enumerate()' quite often. 
  enumerate() takes an iterator and returns an iterator that spits out 
(count,value) tuples.

--bb