Better AAs

[w0rp via Digitalmars-d]

I wrote my own hashmap a little while ago for fun, and also 
because I couldn't get @safe pure nothrow ranges through maps at 
the time, and it turned out that I could also add in @nogc too 
for the ranges and a lot of functions, so I could make a lot of 
my graph types also provide the same guarantees.

https://github.com/w0rp/dstruct/blob/master/source/dstruct/map.d

Maybe there's something in there which might be useful to someone 
else. Maybe I did something horribly wrong for which I must be 
punished.

One thing I did find interesting is the results I got from 
following the OpenJDK method of computing an index in the bucket 
with hash & (length - 1). Because my bucket lengths are always 
powers of 2, the 'bitwise and' achieves fairly uniform 
distribution from what I can tell without needing to execute 
division, which can be slow.