associative arrays: iteration is finally here

[Lars T. Kyllingstad]

Pelle Månsson wrote:
> Lars T. Kyllingstad wrote:
>> Pelle Månsson wrote:
>>> Andrei Alexandrescu wrote:
>>>> Pelle Månsson wrote:
>>>>> Also, foreach with a single variable should default to keys, in my 
>>>>> opinion.
>>>>
>>>> That is debatable as it would make the same code do different things 
>>>> for e.g. vectors and sparse vectors.
>>>>
>>>>
>>>> Andrei
>>>
>>> Debatable indeed, but I find myself using either just the keys or the 
>>> keys and values together, rarely just the values. Maybe that's just me.
>>
>>
>> I've used iteration over values more often than iteration over keys.
>>
>> Besides, I think consistency is important. Since the default for an 
>> ordinary array is to iterate over the values, it should be the same 
>> for associative arrays.
>>
>> -Lars
> I don't understand this, when do you want the values without the keys? 
> If you do, shouldn't you be using a regular array?

Here's an example:

    class SomeObject { ... }
    void doStuffWith(SomeObject s) { ... }
    void doOtherStuffWith(SomeObject s) { ... }

    // Make a collection of objects indexed by ID strings.
    SomeObject[string] myObjects;
    ...

    // First I just want to do something with one of the
    // objects, namely the one called "foo".
    doStuffWith(myObjects["foo"]);

    // Then, I want to do something with all the objects.
    foreach (obj; myObjects)  doOtherStuffWith(obj);

Of course, if iteration was over keys instead of values, I'd just write

    foreach (id, obj; myObjects)  doOtherStuffWith(obj);

But then again, right now, when iteration is over values and I want the 
keys I can just write the same thing. It all comes down to preference, 
and I prefer things the way they are now. :)


> Actually, it doesn't matter all that much, as long as we get .keys and 
> .values as alternatives.

I still think the default for foreach should be consistent with normal 
arrays.

-Lars