Re: Proposal: Make intersperse lazier

24 Sep 2010


      Am 24.09.2010 17:55, schrieb Christian Maeder:
...
I consider it useful, because the "natural" implementation:
prependToAll s = foldr (\ x r -> s : x : r) []
seems to leak without optimization.
"leak" is wrong. My Benchmarks fail without optimization.
(see attached log.txt)

Christian

Bench.hs:

import Criterion.Main

testCase f = print . length . f ','

main = do
  let s = replicate 100000000 'A'
  print $ length s
  defaultMain [ bench "prepend" $ testCase prepend s
              , bench "prependToAll" $ testCase prependToAll s ]

prependToAll :: a -> [a] -> [a]
prependToAll s = foldr (\ x r -> s : x : r) []

prepend :: a -> [a] -> [a]
prepend s l = case l of
  [] -> []
  x : r -> s : x : prepend s r