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.