argument order of functions in Data.Bits
lemming at henning-thielemann.de
Thu Apr 7 08:23:08 EDT 2005
On Thu, 7 Apr 2005, Malcolm Wallace wrote:
> "Simon Marlow" <simonmar at microsoft.com> writes:
>>> shiftL 2 . clearBit 7 . setBit 4 . setBit 1
>>> instead of
>>> flip shiftL 2 . flip clearBit 7 . flip setBit 4 . flip setBit 1
>>> (`shiftL` 2) . (`clearBit` 7) . (`setBit` 4) . (`setBit` 1)
>> On the whole I agree, but I'm inclined against changing this because it
>> would break so much code gratuitously. I vote for just putting this
>> down to a small mistake in the original design, and leaving it. If
>> there's overwhelming support for the change of course we'll make it, but
>> I doubt there will be.
> For what it's worth, the old library NHC.Bits
> implements the 'set' and 'clear' operations with arguments the natural
> way round, although the left and right shift have the same order as
> Data.Bits and the C language.
If both infix operators and alphanumeric function names exist, then one
could use different orders as it is done for 'subtract' and '(-)'.
> I slightly prefer the NHC names ^>>
> and ^<< for shifting too, since they are naturally infix. Henning's
> example composition would look like this:
> (^<< 2) . clear 7 . set 4 . set 1
Indeed, removing the 'Bit' suffix from the bit functions would also be
nice. That would promote the use of qualification, that is Bit.clear,
Bit.set and so on.
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