Pre-expanding alloc cell(s) / reserving space for an associative array

[Cecil Ward]

Before I posted a question about avoiding unnecessary 
allocs/reallocs when adding entries to an array like so
     uint[ dstring ]  arr;

when I build it up from nothing with successive insertions.

The array is accessed by a key that is a dstring. I was told that 
I can’t use .reserve or the like on it? Is that correct? My 
memory fails me, powerful pain drugs.

Is there an alternate method I could use ? To be honest, the 
number of entries is likely to be extremely modest, so this is 
not a huge performance issue, six entries would be considered 
quite a lot. The string keys are probably not very very long. But 
I’m learning good habits for the day when I might have a bigger 
such database.