Functional syntax (Was: RE: [mercury-users] Hi, and determinism)

[Fergus Henderson]

On 02-Feb-2001, Robert Bossy <bossy at ccr.jussieu.fr> wrote:
> Fergus Henderson a écrit :
> > 
> > On 31-Jan-2001, Mattias Waldau <mattias.waldau at abc.se> wrote:
> > > The beatty of Ocaml is that it can do anything a low-level language like C
> > > can - and almost as fast - and that you can make pure programs.
> > 
> > Does Ocaml have support for bit fields, or something equivalent?
> 
> Yes, look for the bitv library that can be found at:
> http://www.lri.fr/~filliatr/ftp/ocaml/ds/
> (files are bitv.ml bitv.mli bitv.ps.gz)

That's not the same.  A bit vector ADT is a useful thing, but it doesn't
help with the kinds of things for which you'd use bit fields in C.

Bit fields are handy for when you have a data type with several fields
that are each less than one word in size, which you want to optimize
for space rather than speed, by packing multiple fields into a single
word.  In ML and Mercury you can achieve that by using integer fields
and manually writing access routines that get and set particular
groups of bits within a word.  But in C you can use bit fields, which
means you don't have to write the bit twiddling access routines.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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