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Add RULES for break on single character #707

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Merged
Bodigrim merged 1 commit into from
Aug 12, 2026
+64 −6
Merged

Add RULES for break on single character #707

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36 changes: 32 additions & 4 deletions src/Data/Text.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -228,7 +228,7 @@ import Prelude (Char, Bool(..), Int, Maybe(..), String,
Eq, (==), (/=), Ord(..), Ordering(..), (++),
Monad(..), pure, Read(..), Show,
(&&), (||), (+), (-), (.), ($), ($!), (>>),
not, return, otherwise, quot)
fst, not, return, otherwise, quot, snd)
import Control.DeepSeq (NFData(rnf))
#if defined(ASSERTS)
import Control.Exception (assert)
Expand Down Expand Up @@ -273,7 +273,7 @@ import qualified Data.Text.Lazy as L
#endif
import Data.Word (Word8)
import Foreign.C.Types
import GHC.Base (eqInt, neInt, gtInt, geInt, ltInt, leInt)
import GHC.Base (eqChar, neChar, eqInt, neInt, gtInt, geInt, ltInt, leInt)
import qualified GHC.Exts as Exts
import GHC.Int (Int8)
import GHC.Stack (HasCallStack)
Expand Down Expand Up @@ -1522,6 +1522,13 @@ takeWhile p t@(Text arr off len) = loop 0
where Iter c d = iter t i
{-# INLINE [1] takeWhile #-}

{-# RULES
"TEXT takeWhile (c `neChar`) -> fst . breakOn (singleton c)" forall c.
takeWhile (c `neChar`) = fst . breakOn (singleton c)
"TEXT takeWhile (`neChar` c) -> fst . breakOn (singleton c)" forall c.
takeWhile (`neChar` c) = fst . breakOn (singleton c)
#-}

-- | /O(n)/ 'takeWhileEnd', applied to a predicate @p@ and a 'Text',
-- returns the longest suffix (possibly empty) of elements that
-- satisfy @p@.
Expand Down Expand Up @@ -1549,6 +1556,13 @@ dropWhile p t@(Text arr off len) = loop 0 0
where Iter c d = iter t i
{-# INLINE [1] dropWhile #-}

{-# RULES
"TEXT dropWhile (c `neChar`) -> snd . breakOn (singleton c)" forall c.
dropWhile (c `neChar`) = snd . breakOn (singleton c)
"TEXT dropWhile (`neChar` c) -> snd . breakOn (singleton c)" forall c.
dropWhile (`neChar` c) = snd . breakOn (singleton c)
#-}

-- | /O(n)/ 'dropWhileEnd' @p@ @t@ returns the prefix remaining after
-- dropping characters that satisfy the predicate @p@ from the end of
-- @t@.
Expand Down Expand Up @@ -1615,7 +1629,14 @@ splitAt n t@(Text arr off len)
span :: (Char -> Bool) -> Text -> (Text, Text)
span p t = case span_ p t of
(# hd,tl #) -> (hd,tl)
{-# INLINE span #-}
{-# INLINE [1] span #-}

{-# RULES
"TEXT span (c `neChar`) -> breakOn (singleton c)" forall c.
span (c `neChar`) = breakOn (singleton c)
"TEXT span (`neChar` c) -> breakOn (singleton c)" forall c.
span (`neChar` c) = breakOn (singleton c)
#-}

-- | /O(n)/ 'break' is like 'span', but the prefix returned is
-- over elements that fail the predicate @p@.
Expand All @@ -1624,7 +1645,14 @@ span p t = case span_ p t of
-- ("180","cm")
break :: (Char -> Bool) -> Text -> (Text, Text)
break p = span (not . p)
{-# INLINE break #-}
{-# INLINE [1] break #-}

{-# RULES
"TEXT break (c `eqChar`) -> breakOn (singleton c)" forall c.
break (c `eqChar`) = breakOn (singleton c)
"TEXT break (`eqChar` c) -> breakOn (singleton c)" forall c.
break (`eqChar` c) = breakOn (singleton c)
#-}

spanEnd :: (Char -> Bool) -> Text -> (Text, Text)
spanEnd = coerce (spanEndM :: (Char -> Identity Bool) -> Text -> Identity (Text, Text))
Expand Down
34 changes: 32 additions & 2 deletions src/Data/Text/Lazy.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -219,7 +219,7 @@ import Prelude (Char, Bool(..), Maybe(..), String,
Eq, (==), Ord(..), Ordering(..), Read(..), Show(showsPrec),
Monad(..), pure, (<$>),
(&&), (+), (-), (.), ($), (++),
error, flip, fmap, fromIntegral, not, otherwise, quot)
error, fst, flip, fmap, fromIntegral, not, otherwise, quot, snd)
import qualified Prelude as P
import Control.Arrow (first)
import Control.DeepSeq (NFData(..))
Expand Down Expand Up @@ -253,6 +253,7 @@ import Data.Text.Lazy.Encoding (decodeUtf8', encodeUtf8Builder)
import Data.Text.Internal.Lazy.Search (indices)
import qualified GHC.CString as GHC
import qualified GHC.Exts as Exts
import GHC.Char (eqChar, neChar)
import GHC.Prim (Addr#)
import GHC.Stack (HasCallStack)
#if __GLASGOW_HASKELL__ >= 914
Expand Down Expand Up @@ -1230,6 +1231,13 @@ takeWhile p t0 = takeWhile' t0
Nothing -> Chunk t (takeWhile' ts)
{-# INLINE [1] takeWhile #-}

{-# RULES
"TEXT takeWhile (c `neChar`) -> fst . breakOn (singleton c)" forall c.
takeWhile (c `neChar`) = fst . breakOn (singleton c)
"TEXT takeWhile (`neChar` c) -> fst . breakOn (singleton c)" forall c.
takeWhile (`neChar` c) = fst . breakOn (singleton c)
#-}

-- | /O(n)/ 'takeWhileEnd', applied to a predicate @p@ and a 'Text',
-- returns the longest suffix (possibly empty) of elements that
-- satisfy @p@.
Expand Down Expand Up @@ -1259,6 +1267,13 @@ dropWhile p t0 = dropWhile' t0
Nothing -> dropWhile' ts
{-# INLINE [1] dropWhile #-}

{-# RULES
"TEXT dropWhile (c `neChar`) -> snd . breakOn (singleton c)" forall c.
dropWhile (c `neChar`) = snd . breakOn (singleton c)
"TEXT dropWhile (`neChar` c) -> snd . breakOn (singleton c)" forall c.
dropWhile (`neChar` c) = snd . breakOn (singleton c)
#-}

-- | /O(n)/ 'dropWhileEnd' @p@ @t@ returns the prefix remaining after
-- dropping characters that satisfy the predicate @p@ from the end of
-- @t@.
Expand Down Expand Up @@ -1435,6 +1450,14 @@ break p t0 = break' t0
Just n | n == 0 -> (Empty, c)
| otherwise -> let (a,b) = T.splitAt n t
in (Chunk a Empty, Chunk b ts)
{-# INLINE [1] break #-}

{-# RULES
"TEXT break (c `eqChar`) -> breakOn (singleton c)" forall c.
break (c `eqChar`) = breakOn (singleton c)
"TEXT break (`eqChar` c) -> breakOn (singleton c)" forall c.
break (`eqChar` c) = breakOn (singleton c)
#-}

-- | /O(n)/ 'span', applied to a predicate @p@ and text @t@, returns
-- a pair whose first element is the longest prefix (possibly empty)
Expand All @@ -1445,7 +1468,14 @@ break p t0 = break' t0
-- ("000","AB")
span :: (Char -> Bool) -> Text -> (Text, Text)
span p = break (not . p)
{-# INLINE span #-}
{-# INLINE [1] span #-}

{-# RULES
"TEXT span (c `neChar`) -> breakOn (singleton c)" forall c.
span (c `neChar`) = breakOn (singleton c)
"TEXT span (`neChar` c) -> breakOn (singleton c)" forall c.
span (`neChar` c) = breakOn (singleton c)
#-}

-- | /O(length of prefix)/ 'spanM', applied to a monadic predicate @p@,
-- a text @t@, returns a pair @(t1, t2)@ where @t1@ is the longest prefix of
Expand Down
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