A while ago, I needed lots of fairly small positive numbers, together with a small number of flags for each, so I thought I'd switch from Int to Word, and map the flags to bits.
Since there are few guarantees about the size of a Word (or Int), surely it would be better to choose a definitely sized basic type, e.g. Word8 or Word16?
Good point in principle, and I would indeed prefer a specific size. Unfortunately, I found just the opposite of this
I vaguely recall that ghc used to generate better code for definitely sized WordN than the generic unguaranteed-size Word.
to be true (although I don't recall whether I checked with IntN or WordN, and I don't have a small example for this issue): Even just replacing Int with Int32 on a system where that should be the same was liable to reduce performance.. Given Don's point about SPECIALI[ZS]E, and the lack of specialisations for IntN/WordN, that might explain it? Claus PS. perhaps on newer 64 bit machines, explicitly selecting 32 bits can offer savings? I'd certainly expect selecting 64 bits on a 32 bit machine to lead to slowdowns.