Efficient M to N conversion on fusion?
Hi, Is there any efficient way to convert M-length ByteString, Text or Vector into N-length one? For example, (a) converting byte array into array of their hex representations. ("abc" => "616263") (b) escaping some specific characters in string. ("a\bc" => "a\\bc") The only way I found is to use concatMap... Thanks, iquiw
On 16 February 2010 21:52, iquiw
Is there any efficient way to convert M-length ByteString, Text or Vector into N-length one?
I don't believe so, no. Maybe the lazy variants would have better efficiency than the strict ones though... -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com Stephen Leacock - "I detest life-insurance agents: they always argue that I shall some day die, which is not so." - http://www.brainyquote.com/quotes/authors/s/stephen_leacock.html
On Tue, Feb 16, 2010 at 07:52:51PM +0900, iquiw wrote:
Is there any efficient way to convert M-length ByteString, Text or Vector into N-length one?
This is just a guess, but in vector at least it should be possible to use sized[1] to tell how much space should be allocated on the final vector. For example, something like the following *untested* code: import qualified Data.Vector.Stream.Monadic as S import qualified Data.Vector.Generic as G import Control.Applicative import Data.Vector.Stream.Size -- | The size should be the size of each v b. concatMapSized :: (G.Vector v a, G.Vector v b) => Size -> (a -> v b) -> v a -> v b concatMapSized size_each f v = let stream = G.stream v size = mult size_each (S.size stream) in G.unstream . flip S.sized size . S.concatMap (G.stream . f) $ stream mult :: Size -> Size -> Size mult (Exact n) (Exact m) = Exact (n*m) mult x y = maybe Max Unknown $ (*) <$> upperBound x <*> upperBound y I really don't know if this would improve or worsen performance, you should check the core and do benchmarks :). [1] http://hackage.haskell.org/packages/archive/vector/0.5/doc/html/Data-Vector-... -- Felipe.
I'll try it, thanks!
iquiw
On Tue, Feb 16, 2010 at 11:12 PM, Felipe Lessa
On Tue, Feb 16, 2010 at 07:52:51PM +0900, iquiw wrote:
Is there any efficient way to convert M-length ByteString, Text or Vector into N-length one?
This is just a guess, but in vector at least it should be possible to use sized[1] to tell how much space should be allocated on the final vector. For example, something like the following *untested* code:
import qualified Data.Vector.Stream.Monadic as S import qualified Data.Vector.Generic as G import Control.Applicative import Data.Vector.Stream.Size
-- | The size should be the size of each v b. concatMapSized :: (G.Vector v a, G.Vector v b) => Size -> (a -> v b) -> v a -> v b concatMapSized size_each f v = let stream = G.stream v size = mult size_each (S.size stream) in G.unstream . flip S.sized size . S.concatMap (G.stream . f) $ stream
mult :: Size -> Size -> Size mult (Exact n) (Exact m) = Exact (n*m) mult x y = maybe Max Unknown $ (*) <$> upperBound x <*> upperBound y
I really don't know if this would improve or worsen performance, you should check the core and do benchmarks :).
[1] http://hackage.haskell.org/packages/archive/vector/0.5/doc/html/Data-Vector-...
-- Felipe. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
participants (3)
-
Felipe Lessa -
iquiw -
Ivan Miljenovic