Straightforward conversion from Int <-> Word

[Julian Seward (Intl Vendor)]

I've found this annoying in the past, and have resorted to hitting
it on the head (GHC-specifically) with a blunt instrument:

   intToNat :: Int -> Word
   intToNat (I# i#) =3D W# (unsafeCast# i#)

This probably defeats the good intentions of the FFI designers,
but it kinda seems like it'll work on all reasonable architectures.

J

| -----Original Message-----
| From: Jan-Willem Maessen [mailto:jmaessen@alum.mit.edu]=20
| Sent: Monday, February 25, 2002 4:46 PM
| To: glasgow-haskell-users@haskell.org
| Subject: Straightforward conversion from Int <-> Word
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| I've cast about a bit and haven't been able to find the appropriate
| functionality, so I'm asking here.
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| I'd like to convert Int32 to and from Word32 in the good old-fashioned
| bitwise fashion (perserving modular arithmetic).  I have the following
| code to show what I mean:
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|   intToNat i
|     | i >=3D 0    =3D fromIntegral i
|     | otherwise =3D fromIntegral (i - minBound) + negBound
|     where negBound =3D fromInteger . negate . toInteger $=20
| (minBound :: Int)
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| One might think that "intToWord32" and "word32ToInt" in lang/Word
| would do what I want---but no!  These are depracated, and I must use
| fromIntegral, which will only perform the conversion correctly for the
| portions of the numeric range which overlap.
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| How do I do the straightforward conversion module 2^32?  I'm sure it's
| buried in there somewhere...  I can't even turn up an appropriate type
| signature, though.
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| -Jan-Willem Maessen
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