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|
{-# LANGUAGE BangPatterns #-}
module Tests.SlowFunctions
(
indices
, splitOn
) where
import qualified Data.Text as T
import Data.Text.Internal (Text(..))
import Data.Text.Unsafe (iter_, unsafeHead, unsafeTail)
indices :: T.Text -- ^ Substring to search for (@needle@)
-> T.Text -- ^ Text to search in (@haystack@)
-> [Int]
indices needle@(Text _narr _noff nlen) haystack@(Text harr hoff hlen)
| T.null needle = []
| otherwise = scan 0
where
scan i | i >= hlen = []
| needle `T.isPrefixOf` t = i : scan (i+nlen)
| otherwise = scan (i+d)
where t = Text harr (hoff+i) (hlen-i)
d = iter_ haystack i
splitOn :: T.Text -- ^ Text to split on
-> T.Text -- ^ Input text
-> [T.Text]
splitOn pat src0
| T.null pat = error "splitOn: empty"
| l == 1 = T.split (== (unsafeHead pat)) src0
| otherwise = go src0
where
l = T.length pat
go src = search 0 src
where
search !n !s
| T.null s = [src] -- not found
| pat `T.isPrefixOf` s = T.take n src : go (T.drop l s)
| otherwise = search (n+1) (unsafeTail s)
|
