[Haskell-cafe] Data.Binary and little endian encoding

[Don Stewart]

timd:
> On a related matter, I am using Data.Binary to serialise data from
> haskell
> for use from other languages. The Data.Binary encoding of a Double is a
> long
> integer for the mantissa, and an int for the exponent.  This doesn't
> work too well for interacting with other languages as I'd need to have
> an arbitrary precision int type there to decode/encode. The CORBA CDR
> standard encodes doubles in a big ended fashion like this (excuse my
> possibly incorrect ascii art):
> 
> 
> | byte | msb                   lsb |
> |------+---------------------------|
> |    0 | S   E6                 E0 |
> |    1 | E10 E9 E8 E7 F3 F2 F1  F0 |
> |    2 | F11                    F4 |
> |    3 | F19                   F12 |
> |    4 | F27                   F20 |
> |    5 | F35                   F28 |
> |    6 | F43                   F36 |
> |    7 | F51                   F44 |
> 
> Up until now, my code is pure haskell.  Is it possible to get at the
> internal bits of a Double/CDouble in ghc? Or Should I use the FFI and
> write C to encode something like the above?

Yep, it's possible, just not portably so. Google for Data.Binary IEEE
discussions.