On Fri, Aug 10, 2007 at 06:12:03PM +0100, Andrew Coppin wrote: > > [big blob of simplifier output] > > Mmm. See, now, I have *no idea* what GHC is saying. But I would have > expected that if I do something like > > x = if testBit 3 q ... > > then the definition of testBit would get inlined, and then hopfully the > optimiser would do something. But then, IANAGD. (I am not a GHC developer.)
Sure, it gets inlined, and you wind up with something like:
x = case 3 .&. (1 `shiftL` q) of
0 -> ...
_ -> ...
or, if you used the (correct and unintuitive) argument order to testBit:
x = case q .&. (1 `shiftL` 3) of
0 -> ...
_ -> ...
We *want* (1 `shiftL` 3) to be reduced to 8 at compile time, but that
doesn't seem to be happening.
(And I'm not a GHC developer either. I should probably start at some
point...)
Stefan
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