isSpace is too slow
ketil at ii.uib.no
Mon May 21 04:43:16 EDT 2007
On Sun, 2007-05-20 at 16:59 +0100, Duncan Coutts wrote:
> isSpace c = c == ' ' ||
> c == '\t' ||
> c == '\n' ||
> c == '\r' ||
> c == '\f' ||
> c == '\v' ||
> c == '\xa0' ||
> iswspace (fromIntegral (ord c)) /= 0
> iswspace does a generic lookup in the unicode property database I think.
So there's little hope of beating iswspace unless your input contains a
lot of spaces, I guess - for all non-space, we call iswspace, which
presumably repeats the tests for ASCII space.
Wouldn't something along these lines be more efficient?
isSpace :: Char -> Bool
isSpace = isSp . ord
isSp c | c <= 13 = c >= 8 -- \b..\r
| c <= 127 = c == 32 -- ' '
| c <= 255 = c == 0xa0 -- nbsp
| otherwise = iswspace(..)
A quick test shows about a factor two improvement
on /usr/share/dict/words, but that will of course only trig the first
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