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{-# LANGUAGE BangPatterns, MagicHash, Rank2Types #-}
-- |
-- Module : Data.Text.Fusion.Common
-- Copyright : (c) Bryan O'Sullivan 2009, 2012
--
-- License : BSD-style
-- Maintainer : bos@serpentine.com, rtomharper@googlemail.com,
-- duncan@haskell.org
-- Stability : experimental
-- Portability : GHC
--
-- Common stream fusion functionality for text.
module Data.Text.Fusion.Common
(
-- * Creation and elimination
singleton
, streamList
, unstreamList
, streamCString#
-- * Basic interface
, cons
, snoc
, append
, head
, uncons
, last
, tail
, init
, null
, lengthI
, compareLengthI
, isSingleton
-- * Transformations
, map
, intercalate
, intersperse
-- ** Case conversion
-- $case
, toCaseFold
, toLower
, toUpper
-- ** Justification
, justifyLeftI
-- * Folds
, foldl
, foldl'
, foldl1
, foldl1'
, foldr
, foldr1
-- ** Special folds
, concat
, concatMap
, any
, all
, maximum
, minimum
-- * Construction
-- ** Scans
, scanl
-- ** Accumulating maps
-- , mapAccumL
-- ** Generation and unfolding
, replicateCharI
, replicateI
, unfoldr
, unfoldrNI
-- * Substrings
-- ** Breaking strings
, take
, drop
, takeWhile
, dropWhile
-- * Predicates
, isPrefixOf
-- * Searching
, elem
, filter
-- * Indexing
, findBy
, indexI
, findIndexI
, countCharI
-- * Zipping and unzipping
, zipWith
) where
import Prelude (Bool(..), Char, Eq(..), Int, Integral, Maybe(..),
Ord(..), Ordering(..), String, (.), ($), (+), (-), (*), (++),
(&&), fromIntegral, otherwise)
import qualified Data.List as L
import qualified Prelude as P
import Data.Bits (shiftL)
import Data.Int (Int64)
import Data.Text.Fusion.Internal
import Data.Text.Fusion.CaseMapping (foldMapping, lowerMapping, upperMapping)
import Data.Text.Fusion.Size
import GHC.Prim (Addr#, chr#, indexCharOffAddr#, ord#)
import GHC.Types (Char(..), Int(..))
singleton :: Char -> Stream Char
singleton c = Stream next False 1
where next False = Yield c True
next True = Done
{-# INLINE singleton #-}
streamList :: [a] -> Stream a
{-# INLINE [0] streamList #-}
streamList s = Stream next s unknownSize
where next [] = Done
next (x:xs) = Yield x xs
unstreamList :: Stream a -> [a]
unstreamList (Stream next s0 _len) = unfold s0
where unfold !s = case next s of
Done -> []
Skip s' -> unfold s'
Yield x s' -> x : unfold s'
{-# INLINE [0] unstreamList #-}
{-# RULES "STREAM streamList/unstreamList fusion" forall s. streamList (unstreamList s) = s #-}
-- | Stream the UTF-8-like packed encoding used by GHC to represent
-- constant strings in generated code.
--
-- This encoding uses the byte sequence "\xc0\x80" to represent NUL,
-- and the string is NUL-terminated.
streamCString# :: Addr# -> Stream Char
streamCString# addr = Stream step 0 unknownSize
where
step !i
| b == 0 = Done
| b <= 0x7f = Yield (C# b#) (i+1)
| b <= 0xdf = let !c = chr $ ((b-0xc0) `shiftL` 6) + next 1
in Yield c (i+2)
| b <= 0xef = let !c = chr $ ((b-0xe0) `shiftL` 12) +
(next 1 `shiftL` 6) +
next 2
in Yield c (i+3)
| otherwise = let !c = chr $ ((b-0xf0) `shiftL` 18) +
(next 1 `shiftL` 12) +
(next 2 `shiftL` 6) +
next 3
in Yield c (i+4)
where b = I# (ord# b#)
next n = I# (ord# (at# (i+n))) - 0x80
b# = at# i
at# (I# i#) = indexCharOffAddr# addr i#
chr (I# i#) = C# (chr# i#)
{-# INLINE [0] streamCString# #-}
-- ----------------------------------------------------------------------------
-- * Basic stream functions
data C s = C0 !s
| C1 !s
-- | /O(n)/ Adds a character to the front of a Stream Char.
cons :: Char -> Stream Char -> Stream Char
cons w (Stream next0 s0 len) = Stream next (C1 s0) (len+1)
where
next (C1 s) = Yield w (C0 s)
next (C0 s) = case next0 s of
Done -> Done
Skip s' -> Skip (C0 s')
Yield x s' -> Yield x (C0 s')
{-# INLINE [0] cons #-}
-- | /O(n)/ Adds a character to the end of a stream.
snoc :: Stream Char -> Char -> Stream Char
snoc (Stream next0 xs0 len) w = Stream next (J xs0) (len+1)
where
next (J xs) = case next0 xs of
Done -> Yield w N
Skip xs' -> Skip (J xs')
Yield x xs' -> Yield x (J xs')
next N = Done
{-# INLINE [0] snoc #-}
data E l r = L !l
| R !r
-- | /O(n)/ Appends one Stream to the other.
append :: Stream Char -> Stream Char -> Stream Char
append (Stream next0 s01 len1) (Stream next1 s02 len2) =
Stream next (L s01) (len1 + len2)
where
next (L s1) = case next0 s1 of
Done -> Skip (R s02)
Skip s1' -> Skip (L s1')
Yield x s1' -> Yield x (L s1')
next (R s2) = case next1 s2 of
Done -> Done
Skip s2' -> Skip (R s2')
Yield x s2' -> Yield x (R s2')
{-# INLINE [0] append #-}
-- | /O(1)/ Returns the first character of a Text, which must be non-empty.
-- Subject to array fusion.
head :: Stream Char -> Char
head (Stream next s0 _len) = loop_head s0
where
loop_head !s = case next s of
Yield x _ -> x
Skip s' -> loop_head s'
Done -> streamError "head" "Empty stream"
{-# INLINE [0] head #-}
-- | /O(1)/ Returns the first character and remainder of a 'Stream
-- Char', or 'Nothing' if empty. Subject to array fusion.
uncons :: Stream Char -> Maybe (Char, Stream Char)
uncons (Stream next s0 len) = loop_uncons s0
where
loop_uncons !s = case next s of
Yield x s1 -> Just (x, Stream next s1 (len-1))
Skip s' -> loop_uncons s'
Done -> Nothing
{-# INLINE [0] uncons #-}
-- | /O(n)/ Returns the last character of a 'Stream Char', which must
-- be non-empty.
last :: Stream Char -> Char
last (Stream next s0 _len) = loop0_last s0
where
loop0_last !s = case next s of
Done -> emptyError "last"
Skip s' -> loop0_last s'
Yield x s' -> loop_last x s'
loop_last !x !s = case next s of
Done -> x
Skip s' -> loop_last x s'
Yield x' s' -> loop_last x' s'
{-# INLINE[0] last #-}
-- | /O(1)/ Returns all characters after the head of a Stream Char, which must
-- be non-empty.
tail :: Stream Char -> Stream Char
tail (Stream next0 s0 len) = Stream next (C0 s0) (len-1)
where
next (C0 s) = case next0 s of
Done -> emptyError "tail"
Skip s' -> Skip (C0 s')
Yield _ s' -> Skip (C1 s')
next (C1 s) = case next0 s of
Done -> Done
Skip s' -> Skip (C1 s')
Yield x s' -> Yield x (C1 s')
{-# INLINE [0] tail #-}
data Init s = Init0 !s
| Init1 {-# UNPACK #-} !Char !s
-- | /O(1)/ Returns all but the last character of a Stream Char, which
-- must be non-empty.
init :: Stream Char -> Stream Char
init (Stream next0 s0 len) = Stream next (Init0 s0) (len-1)
where
next (Init0 s) = case next0 s of
Done -> emptyError "init"
Skip s' -> Skip (Init0 s')
Yield x s' -> Skip (Init1 x s')
next (Init1 x s) = case next0 s of
Done -> Done
Skip s' -> Skip (Init1 x s')
Yield x' s' -> Yield x (Init1 x' s')
{-# INLINE [0] init #-}
-- | /O(1)/ Tests whether a Stream Char is empty or not.
null :: Stream Char -> Bool
null (Stream next s0 _len) = loop_null s0
where
loop_null !s = case next s of
Done -> True
Yield _ _ -> False
Skip s' -> loop_null s'
{-# INLINE[0] null #-}
-- | /O(n)/ Returns the number of characters in a string.
lengthI :: Integral a => Stream Char -> a
lengthI (Stream next s0 _len) = loop_length 0 s0
where
loop_length !z s = case next s of
Done -> z
Skip s' -> loop_length z s'
Yield _ s' -> loop_length (z + 1) s'
{-# INLINE[0] lengthI #-}
-- | /O(n)/ Compares the count of characters in a string to a number.
-- Subject to fusion.
--
-- This function gives the same answer as comparing against the result
-- of 'lengthI', but can short circuit if the count of characters is
-- greater than the number, and hence be more efficient.
compareLengthI :: Integral a => Stream Char -> a -> Ordering
compareLengthI (Stream next s0 len) n =
case exactly len of
Nothing -> loop_cmp 0 s0
Just i -> compare (fromIntegral i) n
where
loop_cmp !z s = case next s of
Done -> compare z n
Skip s' -> loop_cmp z s'
Yield _ s' | z > n -> GT
| otherwise -> loop_cmp (z + 1) s'
{-# INLINE[0] compareLengthI #-}
-- | /O(n)/ Indicate whether a string contains exactly one element.
isSingleton :: Stream Char -> Bool
isSingleton (Stream next s0 _len) = loop 0 s0
where
loop !z s = case next s of
Done -> z == (1::Int)
Skip s' -> loop z s'
Yield _ s'
| z >= 1 -> False
| otherwise -> loop (z+1) s'
{-# INLINE[0] isSingleton #-}
-- ----------------------------------------------------------------------------
-- * Stream transformations
-- | /O(n)/ 'map' @f @xs is the Stream Char obtained by applying @f@
-- to each element of @xs@.
map :: (Char -> Char) -> Stream Char -> Stream Char
map f (Stream next0 s0 len) = Stream next s0 len
where
next !s = case next0 s of
Done -> Done
Skip s' -> Skip s'
Yield x s' -> Yield (f x) s'
{-# INLINE [0] map #-}
{-#
RULES "STREAM map/map fusion" forall f g s.
map f (map g s) = map (\x -> f (g x)) s
#-}
data I s = I1 !s
| I2 !s {-# UNPACK #-} !Char
| I3 !s
-- | /O(n)/ Take a character and place it between each of the
-- characters of a 'Stream Char'.
intersperse :: Char -> Stream Char -> Stream Char
intersperse c (Stream next0 s0 len) = Stream next (I1 s0) len
where
next (I1 s) = case next0 s of
Done -> Done
Skip s' -> Skip (I1 s')
Yield x s' -> Skip (I2 s' x)
next (I2 s x) = Yield x (I3 s)
next (I3 s) = case next0 s of
Done -> Done
Skip s' -> Skip (I3 s')
Yield x s' -> Yield c (I2 s' x)
{-# INLINE [0] intersperse #-}
-- ----------------------------------------------------------------------------
-- ** Case conversions (folds)
-- $case
--
-- With Unicode text, it is incorrect to use combinators like @map
-- toUpper@ to case convert each character of a string individually.
-- Instead, use the whole-string case conversion functions from this
-- module. For correctness in different writing systems, these
-- functions may map one input character to two or three output
-- characters.
caseConvert :: (forall s. Char -> s -> Step (CC s) Char)
-> Stream Char -> Stream Char
caseConvert remap (Stream next0 s0 len) = Stream next (CC s0 '\0' '\0') len
where
next (CC s '\0' _) =
case next0 s of
Done -> Done
Skip s' -> Skip (CC s' '\0' '\0')
Yield c s' -> remap c s'
next (CC s a b) = Yield a (CC s b '\0')
-- | /O(n)/ Convert a string to folded case. This function is mainly
-- useful for performing caseless (or case insensitive) string
-- comparisons.
--
-- A string @x@ is a caseless match for a string @y@ if and only if:
--
-- @toCaseFold x == toCaseFold y@
--
-- The result string may be longer than the input string, and may
-- differ from applying 'toLower' to the input string. For instance,
-- the Armenian small ligature men now (U+FB13) is case folded to the
-- bigram men now (U+0574 U+0576), while the micro sign (U+00B5) is
-- case folded to the Greek small letter letter mu (U+03BC) instead of
-- itself.
toCaseFold :: Stream Char -> Stream Char
toCaseFold = caseConvert foldMapping
{-# INLINE [0] toCaseFold #-}
-- | /O(n)/ Convert a string to upper case, using simple case
-- conversion. The result string may be longer than the input string.
-- For instance, the German eszett (U+00DF) maps to the two-letter
-- sequence SS.
toUpper :: Stream Char -> Stream Char
toUpper = caseConvert upperMapping
{-# INLINE [0] toUpper #-}
-- | /O(n)/ Convert a string to lower case, using simple case
-- conversion. The result string may be longer than the input string.
-- For instance, the Latin capital letter I with dot above (U+0130)
-- maps to the sequence Latin small letter i (U+0069) followed by
-- combining dot above (U+0307).
toLower :: Stream Char -> Stream Char
toLower = caseConvert lowerMapping
{-# INLINE [0] toLower #-}
justifyLeftI :: Integral a => a -> Char -> Stream Char -> Stream Char
justifyLeftI k c (Stream next0 s0 len) =
Stream next (s0 :*: S1 :*: 0) (larger (fromIntegral k) len)
where
next (s :*: S1 :*: n) =
case next0 s of
Done -> next (s :*: S2 :*: n)
Skip s' -> Skip (s' :*: S1 :*: n)
Yield x s' -> Yield x (s' :*: S1 :*: n+1)
next (s :*: S2 :*: n)
| n < k = Yield c (s :*: S2 :*: n+1)
| otherwise = Done
{-# INLINE next #-}
{-# INLINE [0] justifyLeftI #-}
-- ----------------------------------------------------------------------------
-- * Reducing Streams (folds)
-- | foldl, applied to a binary operator, a starting value (typically the
-- left-identity of the operator), and a Stream, reduces the Stream using the
-- binary operator, from left to right.
foldl :: (b -> Char -> b) -> b -> Stream Char -> b
foldl f z0 (Stream next s0 _len) = loop_foldl z0 s0
where
loop_foldl z !s = case next s of
Done -> z
Skip s' -> loop_foldl z s'
Yield x s' -> loop_foldl (f z x) s'
{-# INLINE [0] foldl #-}
-- | A strict version of foldl.
foldl' :: (b -> Char -> b) -> b -> Stream Char -> b
foldl' f z0 (Stream next s0 _len) = loop_foldl' z0 s0
where
loop_foldl' !z !s = case next s of
Done -> z
Skip s' -> loop_foldl' z s'
Yield x s' -> loop_foldl' (f z x) s'
{-# INLINE [0] foldl' #-}
-- | foldl1 is a variant of foldl that has no starting value argument,
-- and thus must be applied to non-empty Streams.
foldl1 :: (Char -> Char -> Char) -> Stream Char -> Char
foldl1 f (Stream next s0 _len) = loop0_foldl1 s0
where
loop0_foldl1 !s = case next s of
Skip s' -> loop0_foldl1 s'
Yield x s' -> loop_foldl1 x s'
Done -> emptyError "foldl1"
loop_foldl1 z !s = case next s of
Done -> z
Skip s' -> loop_foldl1 z s'
Yield x s' -> loop_foldl1 (f z x) s'
{-# INLINE [0] foldl1 #-}
-- | A strict version of foldl1.
foldl1' :: (Char -> Char -> Char) -> Stream Char -> Char
foldl1' f (Stream next s0 _len) = loop0_foldl1' s0
where
loop0_foldl1' !s = case next s of
Skip s' -> loop0_foldl1' s'
Yield x s' -> loop_foldl1' x s'
Done -> emptyError "foldl1"
loop_foldl1' !z !s = case next s of
Done -> z
Skip s' -> loop_foldl1' z s'
Yield x s' -> loop_foldl1' (f z x) s'
{-# INLINE [0] foldl1' #-}
-- | 'foldr', applied to a binary operator, a starting value (typically the
-- right-identity of the operator), and a stream, reduces the stream using the
-- binary operator, from right to left.
foldr :: (Char -> b -> b) -> b -> Stream Char -> b
foldr f z (Stream next s0 _len) = loop_foldr s0
where
loop_foldr !s = case next s of
Done -> z
Skip s' -> loop_foldr s'
Yield x s' -> f x (loop_foldr s')
{-# INLINE [0] foldr #-}
-- | foldr1 is a variant of 'foldr' that has no starting value argument,
-- and thus must be applied to non-empty streams.
-- Subject to array fusion.
foldr1 :: (Char -> Char -> Char) -> Stream Char -> Char
foldr1 f (Stream next s0 _len) = loop0_foldr1 s0
where
loop0_foldr1 !s = case next s of
Done -> emptyError "foldr1"
Skip s' -> loop0_foldr1 s'
Yield x s' -> loop_foldr1 x s'
loop_foldr1 x !s = case next s of
Done -> x
Skip s' -> loop_foldr1 x s'
Yield x' s' -> f x (loop_foldr1 x' s')
{-# INLINE [0] foldr1 #-}
intercalate :: Stream Char -> [Stream Char] -> Stream Char
intercalate s = concat . (L.intersperse s)
{-# INLINE [0] intercalate #-}
-- ----------------------------------------------------------------------------
-- ** Special folds
-- | /O(n)/ Concatenate a list of streams. Subject to array fusion.
concat :: [Stream Char] -> Stream Char
concat = L.foldr append empty
{-# INLINE [0] concat #-}
-- | Map a function over a stream that results in a stream and concatenate the
-- results.
concatMap :: (Char -> Stream Char) -> Stream Char -> Stream Char
concatMap f = foldr (append . f) empty
{-# INLINE [0] concatMap #-}
-- | /O(n)/ any @p @xs determines if any character in the stream
-- @xs@ satisifes the predicate @p@.
any :: (Char -> Bool) -> Stream Char -> Bool
any p (Stream next0 s0 _len) = loop_any s0
where
loop_any !s = case next0 s of
Done -> False
Skip s' -> loop_any s'
Yield x s' | p x -> True
| otherwise -> loop_any s'
{-# INLINE [0] any #-}
-- | /O(n)/ all @p @xs determines if all characters in the 'Text'
-- @xs@ satisify the predicate @p@.
all :: (Char -> Bool) -> Stream Char -> Bool
all p (Stream next0 s0 _len) = loop_all s0
where
loop_all !s = case next0 s of
Done -> True
Skip s' -> loop_all s'
Yield x s' | p x -> loop_all s'
| otherwise -> False
{-# INLINE [0] all #-}
-- | /O(n)/ maximum returns the maximum value from a stream, which must be
-- non-empty.
maximum :: Stream Char -> Char
maximum (Stream next0 s0 _len) = loop0_maximum s0
where
loop0_maximum !s = case next0 s of
Done -> emptyError "maximum"
Skip s' -> loop0_maximum s'
Yield x s' -> loop_maximum x s'
loop_maximum !z !s = case next0 s of
Done -> z
Skip s' -> loop_maximum z s'
Yield x s'
| x > z -> loop_maximum x s'
| otherwise -> loop_maximum z s'
{-# INLINE [0] maximum #-}
-- | /O(n)/ minimum returns the minimum value from a 'Text', which must be
-- non-empty.
minimum :: Stream Char -> Char
minimum (Stream next0 s0 _len) = loop0_minimum s0
where
loop0_minimum !s = case next0 s of
Done -> emptyError "minimum"
Skip s' -> loop0_minimum s'
Yield x s' -> loop_minimum x s'
loop_minimum !z !s = case next0 s of
Done -> z
Skip s' -> loop_minimum z s'
Yield x s'
| x < z -> loop_minimum x s'
| otherwise -> loop_minimum z s'
{-# INLINE [0] minimum #-}
-- -----------------------------------------------------------------------------
-- * Building streams
scanl :: (Char -> Char -> Char) -> Char -> Stream Char -> Stream Char
scanl f z0 (Stream next0 s0 len) = Stream next (S1 :*: z0 :*: s0) (len+1) -- HINT maybe too low
where
{-# INLINE next #-}
next (S1 :*: z :*: s) = Yield z (S2 :*: z :*: s)
next (S2 :*: z :*: s) = case next0 s of
Yield x s' -> let !x' = f z x
in Yield x' (S2 :*: x' :*: s')
Skip s' -> Skip (S2 :*: z :*: s')
Done -> Done
{-# INLINE [0] scanl #-}
-- -----------------------------------------------------------------------------
-- ** Accumulating maps
{-
-- | /O(n)/ Like a combination of 'map' and 'foldl'. Applies a
-- function to each element of a stream, passing an accumulating
-- parameter from left to right, and returns a final stream.
--
-- /Note/: Unlike the version over lists, this function does not
-- return a final value for the accumulator, because the nature of
-- streams precludes it.
mapAccumL :: (a -> b -> (a,b)) -> a -> Stream b -> Stream b
mapAccumL f z0 (Stream next0 s0 len) = Stream next (s0 :*: z0) len -- HINT depends on f
where
{-# INLINE next #-}
next (s :*: z) = case next0 s of
Yield x s' -> let (z',y) = f z x
in Yield y (s' :*: z')
Skip s' -> Skip (s' :*: z)
Done -> Done
{-# INLINE [0] mapAccumL #-}
-}
-- -----------------------------------------------------------------------------
-- ** Generating and unfolding streams
replicateCharI :: Integral a => a -> Char -> Stream Char
replicateCharI n c
| n < 0 = empty
| otherwise = Stream next 0 (fromIntegral n) -- HINT maybe too low
where
next i | i >= n = Done
| otherwise = Yield c (i + 1)
{-# INLINE [0] replicateCharI #-}
data RI s = RI !s {-# UNPACK #-} !Int64
replicateI :: Int64 -> Stream Char -> Stream Char
replicateI n (Stream next0 s0 len) =
Stream next (RI s0 0) (fromIntegral (max 0 n) * len)
where
next (RI s k)
| k >= n = Done
| otherwise = case next0 s of
Done -> Skip (RI s0 (k+1))
Skip s' -> Skip (RI s' k)
Yield x s' -> Yield x (RI s' k)
{-# INLINE [0] replicateI #-}
-- | /O(n)/, where @n@ is the length of the result. The unfoldr function
-- is analogous to the List 'unfoldr'. unfoldr builds a stream
-- from a seed value. The function takes the element and returns
-- Nothing if it is done producing the stream or returns Just
-- (a,b), in which case, a is the next Char in the string, and b is
-- the seed value for further production.
unfoldr :: (a -> Maybe (Char,a)) -> a -> Stream Char
unfoldr f s0 = Stream next s0 1 -- HINT maybe too low
where
{-# INLINE next #-}
next !s = case f s of
Nothing -> Done
Just (w, s') -> Yield w s'
{-# INLINE [0] unfoldr #-}
-- | /O(n)/ Like 'unfoldr', 'unfoldrNI' builds a stream from a seed
-- value. However, the length of the result is limited by the
-- first argument to 'unfoldrNI'. This function is more efficient than
-- 'unfoldr' when the length of the result is known.
unfoldrNI :: Integral a => a -> (b -> Maybe (Char,b)) -> b -> Stream Char
unfoldrNI n f s0 | n < 0 = empty
| otherwise = Stream next (0 :*: s0) (fromIntegral (n*2)) -- HINT maybe too high
where
{-# INLINE next #-}
next (z :*: s) = case f s of
Nothing -> Done
Just (w, s') | z >= n -> Done
| otherwise -> Yield w ((z + 1) :*: s')
{-# INLINE unfoldrNI #-}
-------------------------------------------------------------------------------
-- * Substreams
-- | /O(n)/ take n, applied to a stream, returns the prefix of the
-- stream of length @n@, or the stream itself if @n@ is greater than the
-- length of the stream.
take :: Integral a => a -> Stream Char -> Stream Char
take n0 (Stream next0 s0 len) =
Stream next (n0 :*: s0) (smaller len (fromIntegral (max 0 n0)))
where
{-# INLINE next #-}
next (n :*: s) | n <= 0 = Done
| otherwise = case next0 s of
Done -> Done
Skip s' -> Skip (n :*: s')
Yield x s' -> Yield x ((n-1) :*: s')
{-# INLINE [0] take #-}
-- | /O(n)/ drop n, applied to a stream, returns the suffix of the
-- stream after the first @n@ characters, or the empty stream if @n@
-- is greater than the length of the stream.
drop :: Integral a => a -> Stream Char -> Stream Char
drop n0 (Stream next0 s0 len) =
Stream next (J n0 :*: s0) (len - fromIntegral (max 0 n0))
where
{-# INLINE next #-}
next (J n :*: s)
| n <= 0 = Skip (N :*: s)
| otherwise = case next0 s of
Done -> Done
Skip s' -> Skip (J n :*: s')
Yield _ s' -> Skip (J (n-1) :*: s')
next (N :*: s) = case next0 s of
Done -> Done
Skip s' -> Skip (N :*: s')
Yield x s' -> Yield x (N :*: s')
{-# INLINE [0] drop #-}
-- | takeWhile, applied to a predicate @p@ and a stream, returns the
-- longest prefix (possibly empty) of elements that satisfy p.
takeWhile :: (Char -> Bool) -> Stream Char -> Stream Char
takeWhile p (Stream next0 s0 len) = Stream next s0 len -- HINT maybe too high
where
{-# INLINE next #-}
next !s = case next0 s of
Done -> Done
Skip s' -> Skip s'
Yield x s' | p x -> Yield x s'
| otherwise -> Done
{-# INLINE [0] takeWhile #-}
-- | dropWhile @p @xs returns the suffix remaining after takeWhile @p @xs.
dropWhile :: (Char -> Bool) -> Stream Char -> Stream Char
dropWhile p (Stream next0 s0 len) = Stream next (S1 :*: s0) len -- HINT maybe too high
where
{-# INLINE next #-}
next (S1 :*: s) = case next0 s of
Done -> Done
Skip s' -> Skip (S1 :*: s')
Yield x s' | p x -> Skip (S1 :*: s')
| otherwise -> Yield x (S2 :*: s')
next (S2 :*: s) = case next0 s of
Done -> Done
Skip s' -> Skip (S2 :*: s')
Yield x s' -> Yield x (S2 :*: s')
{-# INLINE [0] dropWhile #-}
-- | /O(n)/ The 'isPrefixOf' function takes two 'Stream's and returns
-- 'True' iff the first is a prefix of the second.
isPrefixOf :: (Eq a) => Stream a -> Stream a -> Bool
isPrefixOf (Stream next1 s1 _) (Stream next2 s2 _) = loop (next1 s1) (next2 s2)
where
loop Done _ = True
loop _ Done = False
loop (Skip s1') (Skip s2') = loop (next1 s1') (next2 s2')
loop (Skip s1') x2 = loop (next1 s1') x2
loop x1 (Skip s2') = loop x1 (next2 s2')
loop (Yield x1 s1') (Yield x2 s2') = x1 == x2 &&
loop (next1 s1') (next2 s2')
{-# INLINE [0] isPrefixOf #-}
{-# SPECIALISE isPrefixOf :: Stream Char -> Stream Char -> Bool #-}
-- ----------------------------------------------------------------------------
-- * Searching
-------------------------------------------------------------------------------
-- ** Searching by equality
-- | /O(n)/ elem is the stream membership predicate.
elem :: Char -> Stream Char -> Bool
elem w (Stream next s0 _len) = loop_elem s0
where
loop_elem !s = case next s of
Done -> False
Skip s' -> loop_elem s'
Yield x s' | x == w -> True
| otherwise -> loop_elem s'
{-# INLINE [0] elem #-}
-------------------------------------------------------------------------------
-- ** Searching with a predicate
-- | /O(n)/ The 'findBy' function takes a predicate and a stream,
-- and returns the first element in matching the predicate, or 'Nothing'
-- if there is no such element.
findBy :: (Char -> Bool) -> Stream Char -> Maybe Char
findBy p (Stream next s0 _len) = loop_find s0
where
loop_find !s = case next s of
Done -> Nothing
Skip s' -> loop_find s'
Yield x s' | p x -> Just x
| otherwise -> loop_find s'
{-# INLINE [0] findBy #-}
-- | /O(n)/ Stream index (subscript) operator, starting from 0.
indexI :: Integral a => Stream Char -> a -> Char
indexI (Stream next s0 _len) n0
| n0 < 0 = streamError "index" "Negative index"
| otherwise = loop_index n0 s0
where
loop_index !n !s = case next s of
Done -> streamError "index" "Index too large"
Skip s' -> loop_index n s'
Yield x s' | n == 0 -> x
| otherwise -> loop_index (n-1) s'
{-# INLINE [0] indexI #-}
-- | /O(n)/ 'filter', applied to a predicate and a stream,
-- returns a stream containing those characters that satisfy the
-- predicate.
filter :: (Char -> Bool) -> Stream Char -> Stream Char
filter p (Stream next0 s0 len) = Stream next s0 len -- HINT maybe too high
where
next !s = case next0 s of
Done -> Done
Skip s' -> Skip s'
Yield x s' | p x -> Yield x s'
| otherwise -> Skip s'
{-# INLINE [0] filter #-}
{-# RULES
"STREAM filter/filter fusion" forall p q s.
filter p (filter q s) = filter (\x -> q x && p x) s
#-}
-- | The 'findIndexI' function takes a predicate and a stream and
-- returns the index of the first element in the stream satisfying the
-- predicate.
findIndexI :: Integral a => (Char -> Bool) -> Stream Char -> Maybe a
findIndexI p s = case findIndicesI p s of
(i:_) -> Just i
_ -> Nothing
{-# INLINE [0] findIndexI #-}
-- | The 'findIndicesI' function takes a predicate and a stream and
-- returns all indices of the elements in the stream satisfying the
-- predicate.
findIndicesI :: Integral a => (Char -> Bool) -> Stream Char -> [a]
findIndicesI p (Stream next s0 _len) = loop_findIndex 0 s0
where
loop_findIndex !i !s = case next s of
Done -> []
Skip s' -> loop_findIndex i s' -- hmm. not caught by QC
Yield x s' | p x -> i : loop_findIndex (i+1) s'
| otherwise -> loop_findIndex (i+1) s'
{-# INLINE [0] findIndicesI #-}
-------------------------------------------------------------------------------
-- * Zipping
-- | zipWith generalises 'zip' by zipping with the function given as
-- the first argument, instead of a tupling function.
zipWith :: (a -> a -> b) -> Stream a -> Stream a -> Stream b
zipWith f (Stream next0 sa0 len1) (Stream next1 sb0 len2) =
Stream next (sa0 :*: sb0 :*: N) (smaller len1 len2)
where
next (sa :*: sb :*: N) = case next0 sa of
Done -> Done
Skip sa' -> Skip (sa' :*: sb :*: N)
Yield a sa' -> Skip (sa' :*: sb :*: J a)
next (sa' :*: sb :*: J a) = case next1 sb of
Done -> Done
Skip sb' -> Skip (sa' :*: sb' :*: J a)
Yield b sb' -> Yield (f a b) (sa' :*: sb' :*: N)
{-# INLINE [0] zipWith #-}
-- | /O(n)/ The 'countCharI' function returns the number of times the
-- query element appears in the given stream.
countCharI :: Integral a => Char -> Stream Char -> a
countCharI a (Stream next s0 _len) = loop 0 s0
where
loop !i !s = case next s of
Done -> i
Skip s' -> loop i s'
Yield x s' | a == x -> loop (i+1) s'
| otherwise -> loop i s'
{-# INLINE [0] countCharI #-}
streamError :: String -> String -> a
streamError func msg = P.error $ "Data.Text.Fusion.Common." ++ func ++ ": " ++ msg
emptyError :: String -> a
emptyError func = internalError func "Empty input"
internalError :: String -> a
internalError func = streamError func "Internal error"
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