how to iterate over an AA by key-value pair (tuple)?

[Steven Schveighoffer]

On Thu, 13 Feb 2014 19:06:45 -0500, timotheecour  
<timothee.cour2 at gmail.com> wrote:

> On Thursday, 13 February 2014 at 23:56:35 UTC, Timothee Cour
> wrote:
>> how to iterate over an AA by key-value pair (tuple)?
>> use case:
>> avoid interrupting UFCS chains, eg:
>> foo.generate_aa.byKeyValue.filter!(a=>a[0].isLower).map!(a=>a[1]) ...
>> of course I could roll my own function but I was wondering if there's
>> already a way.
>
>
> is there anything more efficient than this?
>
> auto byKeyValue(T)(T a)if(isAssociativeArray!T){
>     return a.byKey.map!(b=>tuple(b, a[b]));
> }

Of course. The a[b] lookup is significant in the complexity, it's  
amortized constant, and the constant is not always small. Consider that  
all keys and values are already stored in structs inside the AA. With  
low-level access, it would be trivial to make an efficient tuple generator  
that did not need to lookup values by keys.

-Steve