bos:
> Jason Dagit wrote:
>
> >I think, given my simple algorithm that means that (==) for
> >ByteStrings is slower than (==) for String. Is this possible?
>
> Yes indeed. Over ByteStrings, (==) is implemented as a call to memcmp.
> For small strings, this loses by a large margin because it has to go
> through the FFI.
>
Yes, a non-memcmp version can sometimes be profitably used here.
Something like this Core:
eq !n (Ptr p) (Ptr q) = inlinePerformIO $ IO $ go n p q
where
go !n p q s
| n == 0 = (# s , True #)
| otherwise = case readInt8OffAddr# p 0# s of
(# s, a #) -> case readInt8OffAddr# q 0# s of
(# s, b #) | a /=# b -> (# s, False #)
| otherwise -> go (n-1) (plusAddr# p 1#)
(plusAddr# q 1#) s
Ok, so that's not Core, but it could be ;)
-- Don
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