Associative array key order

[bearophile]

> I remember there is a trick to find the address of a D 
> associative array key given its value address,

Perhaps you need a better explanation for that. Let's say your 
data structure is:


final class OrderedAA(TK, TV) {
     struct MV {
         TV item;
         MV* pred, succ;
     }
     private MV[TK] data;
     ...
}

it's a wrapper to a built-in associative array. Each value is a 
struct that beside the original value contains a pointer to the 
precedent and successive MV, in a doubly linked list.

The member functions of OrderedAA that add or remove items from 
the associative array manage the linked list of values. The 
iteration is a range that follows the linked list. But this way 
you only scan the values... To also scan keys or key-val pairs 
you have to find the pointer to the key.

Maybe it's worth adding in Bugzilla an ehnancement request for a 
portable way to find that pointer... to implement a hash-based 
ordered associative array in library code.

Bye,
bearophile