Sets / associative arrays with void values?

[Jeff M]

On 2007-01-06 16:05:06 -0800, "Vladimir Panteleev" 
<tehcybershadow at gmail.com> said:

> I've been wondering whether D supported sets, or something similar. 
> What I  have in mind isn't unlike associative arrays, but without 
> values: an  unordered list with quick look-up and simple 
> addition/removal of elements,  yet still capable of enumeration, etc.
> 
> I followed my intuition and tried to declare an associative array with 
> a  "void" value type:
> 
> void[int] foo;
> 
> To my surprise, it compiled. And even the "in" operation and the .keys 
> and  .values properties worked fine (or as fine as they can work with 
> an empty  associative array).
> 
> Of course, the question comes: how would one add keys to such a 
> construct?  The practical answer is obvious: use a real "dummy" data 
> type (bit, for  example) as the value type, but I find it a shame that 
> declaring such  constructs is allowed - yet you can't really use them.

It would be nice if a "void[int]" array was usable. Associative arrays 
are create-on-access, so "foo[5];" should be a legal for creating an 
index in the array, but this throws an error.

-- Jeff