Trying to implement some random function I encountered this:
uint randFunc(uint x)
{
static uint[uint] vals;
if (auto r = x in vals) return *r;
return vals[x] = uniform!uint();
}
I have to lookup x twice and it seems that there is no way around
it. Can't I tell the AA to set a value for a given key if it
doesn't already have one
(1) with only one lookup, and
(2) in a safe way?
For the semantics, that should behave like this:
V set(K, V)(ref const(V)[const(K)] aa, auto ref const(K) key,
lazy const(V) value)
{
if (auto valPtr = key in aa) return *valPtr;
// cast away const as initialization is okay:
return (cast() aa[key]) = value();
}
The function is dual to AA's get.
It would make it possible for an AA with const value type to have
values added which is perfectly fine for arrays. All I have seen
so far, one cannot safely add values to them as initialization
and assignment cannot be distinguished.
