On Tue, Sep 21, 2010 at 12:08, Daniel Fischer <daniel.is.fisc...@web.de> wrote: >> Endianness only matters when marshaling bytes into a single value -- >> Data.Binary.Get/Put handles that. Once the data is encoded as a Word, >> endianness is no longer relevant. > > I mean, take e.g. 2^62 :: Word64. If you poke that to memory, on a big- > endian machine, you'd get the byte sequence > 40 00 00 00 00 00 00 00 > while on a little-endian, you'd get > 00 00 00 00 00 00 00 40 > , right? > > If both bit-patterns are interpreted the same as doubles, sign-bit = 0, > exponent-bits = 0x400 = 1024, mantissa = 0 , thus yielding > 1.0*2^(1024 - 1023) = 2.0, fine. But if on a little-endian machine, the > floating point handling is not little-endian and the number is interpreted > as sign-bit = 0, exponent-bits = 0, mantissa = 0x40, hence > (1 + 2^(-46))*2^(-1023), havoc. > > I simply didn't know whether that could happen. According to > http://en.wikipedia.org/wiki/Endianness#Floating-point_and_endianness it > could. > On the other hand, "no standard for transferring floating point values has > been made. This means that floating point data written on one machine may > not be readable on another", so if it breaks on weird machines, it's at > least a general problem (and not Haskell's).
Oh, I misunderstood the question -- you're asking about architectures on which floating-point and fixed-point numbers use a different endianness? I don't think it's worth worrying about, unless you want to use Haskell for number crunching on a PDP-11. If you do need to implement IEEE754 parsing for unusual endians (like 3-4-1-2), parse the word yourself and then use 'wordToFloat' and friends to convert it. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
