On Mar 19, 2010, at 16:41 , ivovnenko wrote:
w :: Eq a => [a] -> [a] -> Int w text str = w' (reverse text) (reverse str) w' :: Eq a => [a] -> [a] -> Int -- Init w' _ [] = 0 w' [] _ = 0 -- For one symbol string w' text [a] = if head text == a then w' (tail text) [a] +1 else w' (tail text) [a]
Couple of suggestions here:
w' (x:xs) s@[a] = w' xs s + (if x == a then 1 else 0)
-- General case w' text str = if head str == head text then w' (tail text) (tail str) + w' (tail text) str else w' (tail text) str
w' (x:xs) s@(a:as) = let next = w' xs s in if x == a then w' xs as + next else next
This will save some function calls by using pattern matching. Combining the common subexpressions probably won't count for much except in terms of elegance. The rest probably comes down to strictness but I'll let more knowledgeable people comment on that :) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH