I think Integer is prefered in Haskell. I mean normally, I should use it in my code. So following my example, why cannot CPid be treated as Integer. Only when it needs to be transfered to C or whatsoever, we convert it to Long or whatsoever. So we have a unified type system, not a bunch of types I need to convert, convert, convert. And, let say using Integer for pid is insane. Then if I do not convert it into Integer, when serialised, I have to point out with Word32/Word64, which is definitely bad.
On Tue, Jun 30, 2009 at 11:01 AM, Ahn, Ki Yung<kya...@gmail.com> wrote: > Magicloud Magiclouds 쓴 글: >> >> Hi, >> There are times, when we need to make some system calls, or call C >> library. So we have to deal with C data types. >> For example, CPid, which is an integer, actually. So we can do >> "fromIntegral pid". Then why do not we define "type CPid = Integer", >> and convert Haskell Integer with C Int internally. So the "user" does >> not have to care about the type convert (everywhere, which is ugly). >> And, specially, when doing something like serialisation, for Haskell >> Integer, the user does not have to do things with precision. But for >> CPid, without the fromIntegral, we have to specify its precision, >> well, on different machine/OS, the precision may not be the same. > > Integer is not a fixed length chunk of bits. It can be arbitrarily large as > long as there is memory left in the system. It's theoretically more clean > being close to a mathematical definition of integers, but internally a > complicated beast. So defining CPid as Integer is just not sane. > > In addition, we cannot use Int either. Int is not a 32 bit or 64 bit word. > The Haskell 98 standard does not require that, and in most implementations > it is 2^31 singed bits using one bit as a mark to distinguish pointers from > values for garbage collection purposes. (OCaml int types are like that too.) > > I hope this gives enough explanation. > > -- > Ahn, Ki Yung > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- 竹密岂妨流水过 山高哪阻野云飞 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
