Associative Ranges

[via Digitalmars-d]

On Sunday, 3 August 2014 at 18:38:51 UTC, Freddy wrote:
> On Sunday, 3 August 2014 at 08:50:47 UTC, Marc Schütz wrote:
>> 3) For the value and key ranges, there should be a guarantee 
>> that they can be zipped through, i.e. that the elements in 
>> them are in the same order so keys and values correspond to 
>> each other. The built-in associative arrays provide `byKey` 
>> and `byValue`, which satisfy this condition.
> Also won't the implicit range make it hard to implement function
> like map (should you map to whole range or to the value)

I guess when you iterate over it, you just get tuples. So, `map` 
would return a normal range of tuples, not an associative range. 
There could then be a method to convert such a range to an 
associative range (although it would need to assume that the 
first tuple elements = keys are unique).

I'm not sure whether this is the right thing to do. In any case I 
don't think it's good to map the keys, because they mustn't be 
modified, or otherwise you could get duplicate keys.

An alternative would be that `map` takes both a the key and the 
value, but returns only the new value. The same goes for the 
other range operations (e.g. reduce). But on the other hand, this 
doesn't seem to scale, because all range algorithms would then 
have to be specialized for associative ranges...