Re: [Haskell-cafe] More idiomatic use of strictness
Don Stewart-2 wrote: I'd use a strict pair and the rnf strategy. data P = P [Something] !Int rnf dfs' (P dfs' (n+1) Thanks all, it definitely seems like an improvement. -- Grzegorz -- View this message in context: http://www.nabble.com/More-idiomatic-use-of-strictness-tp18379800p18403657.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] More idiomatic use of strictness
Hi all,
Is there a less ugly way of avoiding laziness in the code pasted below then
the use of seq in the last line?
The program is supposed to split a large input file into chunks and check in
how many of those chunks each of a list of words appear, as well as the
total number of chunks. Without the seq it consumes huge amounts of memory.
Thanks!
Grzegorz
{-# LANGUAGE BangPatterns, PatternGuards #-}
import Data.List (foldl')
split delim s
| [] - rest = [token]
| otherwise = token : split delim (tail rest)
where (token,rest) = span (/=delim) s
main = do
putStrLn = fmap (show . stats [the,a,and] . split DOC . words)
getContents
stats ws docs = foldl' f ((map (const 0) ws),0) docs
where f (dfs,n) d = let dfs' = zipWith (\w df - (df + fromEnum (w
`elem` d))) ws dfs
in sum dfs' `seq` (dfs',n+1)
--
View this message in context:
http://www.nabble.com/More-idiomatic-use-of-strictness-tp18379800p18379800.html
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Re: [Haskell-cafe] More idiomatic use of strictness
Hi all, Op Thursday 10 July 2008 12:16:25 schreef Grzegorz Chrupala: Is there a less ugly way of avoiding laziness in the code pasted below then the use of seq in the last line? You could replace the list dfs' with a strict list type, like: data StrictList a = Cons !a !(StrictList a) | Nil Then you wouldn't have to make useless calls to sum and seq to force strictness. It would be more work though because you'd have to define your own higher order functions to work with the strict list. Reinier signature.asc Description: This is a digitally signed message part. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] More idiomatic use of strictness
On Thu, 2008-07-10 at 03:16 -0700, Grzegorz Chrupala wrote:
Hi all,
Is there a less ugly way of avoiding laziness in the code pasted below then
the use of seq in the last line?
The program is supposed to split a large input file into chunks and check in
how many of those chunks each of a list of words appear, as well as the
total number of chunks. Without the seq it consumes huge amounts of memory.
Strategies! Try
((,) $| rnf) dfs' (n + 1)
Or
(id $| seqPair rnf r0) (dfs', n + 1)
But I don't know if that falls within the intended meaning of `less
ugly'.
jcc
{-# LANGUAGE BangPatterns, PatternGuards #-}
import Data.List (foldl')
split delim s
| [] - rest = [token]
| otherwise = token : split delim (tail rest)
where (token,rest) = span (/=delim) s
main = do
putStrLn = fmap (show . stats [the,a,and] . split DOC . words)
getContents
stats ws docs = foldl' f ((map (const 0) ws),0) docs
where f (dfs,n) d = let dfs' = zipWith (\w df - (df + fromEnum (w
`elem` d))) ws dfs
in sum dfs' `seq` (dfs',n+1)
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Re: [Haskell-cafe] More idiomatic use of strictness
jonathanccast: On Thu, 2008-07-10 at 03:16 -0700, Grzegorz Chrupala wrote: Hi all, Is there a less ugly way of avoiding laziness in the code pasted below then the use of seq in the last line? The program is supposed to split a large input file into chunks and check in how many of those chunks each of a list of words appear, as well as the total number of chunks. Without the seq it consumes huge amounts of memory. Strategies! Try ((,) $| rnf) dfs' (n + 1) Or (id $| seqPair rnf r0) (dfs', n + 1) But I don't know if that falls within the intended meaning of `less ugly'. I'd use a strict pair and the rnf strategy. data P = P [Something] !Int rnf dfs' (P dfs' (n+1) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
