Converting things to and from binary

George Russell
Tue, 20 May 2003 13:32:02 +0200

Derek wrote (snipped)
 > What's wrong with NHC's Binary/BinArray library?  There seems to be a
 > GHC port on the GreenCard page.

The home page of the York Binary library seems to be
Malcolm will doubtless have something to say here.  However I would
say not that there's something "wrong" with the Binary/BinArray
library, but that it seems to be addressed towards a different
class of problems (specifically data-compression) to those
I am interested in (blasting data rapidly in and out).  The main
differences are
(1) the framework I proposed in the original message:
is byte-based, while the York Binary framework is bit-based.
I would imagine that this means the York Binary framework would be
very much less efficient at handling long sequences of bytes,
since they will presumably have to be shifted before
being written to the destination.
(2) the York Binary library uses the IO monad, and presumably
various variables within a BinHandle, to keep track of state.
I think this is unnecessary, for example I don't think the
process of converting a value to a byte array should really
have to go through IO.  We are supposed to be functional
programmers after all.
(3) the York binary library provides two things you can
write bits to (a Handle, and a fixed area in memory) and a
large set of operations (seek and co), but it would be
difficult for a normal programmer to extend this.  (For
example, what about someone in GHC wanting to write to
a Posix Fd?)  On the other hand the framework I propose
has only two basic operations for writing, and two for
reading, which means it should be much easier to define
alternative consumers and sources of binary data.