X-Git-Url: https://git.immae.eu/?a=blobdiff_plain;f=Pipes%2FText.hs;h=f71f17f77528b2acbaa7b1785d5cf54e2c0b96d7;hb=89cf7024a1ea56acdb7c39581141ecc9de1dc031;hp=d62aee7af6eeb34d4651033223a56ccb0034c71a;hpb=c9d1c945a4343d756533b85060c35c04be0c8b02;p=github%2Ffretlink%2Ftext-pipes.git

diff --git a/Pipes/Text.hs b/Pipes/Text.hs
index d62aee7..f71f17f 100644
--- a/Pipes/Text.hs
+++ b/Pipes/Text.hs
@@ -1,178 +1,104 @@
-{-# LANGUAGE RankNTypes, TypeFamilies, NoMonomorphismRestriction #-}
-
-{-| This module provides @pipes@ utilities for \"text streams\", which are
-    streams of 'Text' chunks.  The individual chunks are uniformly @strict@, but 
-    a 'Producer' can be converted to and from lazy 'Text's; an 'IO.Handle' can
-    be associated with a 'Producer' or 'Consumer' according as it is read or written to.
-
-    To stream to or from 'IO.Handle's, one can use 'fromHandle' or 'toHandle'.  For
-    example, the following program copies a document from one file to another:
-
-> import Pipes
-> import qualified Data.Text.Pipes as Text
-> import System.IO
->
-> main =
->     withFile "inFile.txt"  ReadMode  $ \hIn  ->
->     withFile "outFile.txt" WriteMode $ \hOut ->
->     runEffect $ Text.fromHandle hIn >-> Text.toHandle hOut
-
-To stream from files, the following is perhaps more Prelude-like (note that it uses Pipes.Safe):
-
-> import Pipes
-> import qualified Data.Text.Pipes as Text
-> import Pipes.Safe
->
-> main = runSafeT $ runEffect $ Text.readFile "inFile.txt" >-> Text.writeFile "outFile.txt"
-
-    You can stream to and from 'stdin' and 'stdout' using the predefined 'stdin'
-    and 'stdout' proxies, as with the following \"echo\" program:
-
-> main = runEffect $ Text.stdin >-> Text.stdout
-
-    You can also translate pure lazy 'TL.Text's to and from proxies:
-
-> main = runEffect $ Text.fromLazy (TL.pack "Hello, world!\n") >-> Text.stdout
-
-    In addition, this module provides many functions equivalent to lazy
-    'Text' functions so that you can transform or fold text streams.  For
-    example, to stream only the first three lines of 'stdin' to 'stdout' you
-    might write:
-
-> import Pipes
-> import qualified Pipes.Text as Text
-> import qualified Pipes.Parse as Parse
->
-> main = runEffect $ takeLines 3 Text.stdin >-> Text.stdout
->   where
->     takeLines n = Text.unlines . Parse.takeFree n . Text.lines
-
-    The above program will never bring more than one chunk of text (~ 32 KB) into
-    memory, no matter how long the lines are.
-
-    Note that functions in this library are designed to operate on streams that
-    are insensitive to text boundaries.  This means that they may freely split
-    text into smaller texts and /discard empty texts/.  However, they will
-    /never concatenate texts/ in order to provide strict upper bounds on memory
-    usage.
+{-# LANGUAGE RankNTypes, TypeFamilies, BangPatterns, Trustworthy #-}
+
+{-| The module @Pipes.Text@ closely follows @Pipes.ByteString@ from 
+    the @pipes-bytestring@ package. A draft tutorial can be found in
+    @Pipes.Text.Tutorial@. 
 -}
 
 module Pipes.Text  (
     -- * Producers
-    fromLazy,
-    stdin,
-    fromHandle,
-    readFile,
-    stdinLn,
-
-    -- * Consumers
-    stdout,
-    stdoutLn,
-    toHandle,
-    writeFile,
+    fromLazy
 
     -- * Pipes
-    map,
-    concatMap,
-    take,
-    drop,
-    takeWhile,
-    dropWhile,
-    filter,
-    scan,
-    encodeUtf8,
-    pack,
-    unpack,
-    toCaseFold,
-    toLower,
-    toUpper,
-    stripStart,
+    , map
+    , concatMap
+    , take
+    , takeWhile
+    , filter
+    , toCaseFold
+    , toLower
+    , toUpper
+    , stripStart
+    , scan
 
     -- * Folds
-    toLazy,
-    toLazyM,
-    fold,
-    head,
-    last,
-    null,
-    length,
-    any,
-    all,
-    maximum,
-    minimum,
-    find,
-    index,
-    count,
-
-    -- * Splitters
-    splitAt,
-    chunksOf,
-    span,
-    break,
-    splitWith,
-    split,
-    groupBy,
-    group,
-    lines,
-    words,
-    decodeUtf8,
-    -- * Transformations
-    intersperse,
-    
-    -- * Joiners
-    intercalate,
-    unlines,
-    unwords,
-
-    -- * Character Parsers
-    -- $parse
-    nextChar,
-    drawChar,
-    unDrawChar,
-    peekChar,
-    isEndOfChars,
+    , toLazy
+    , toLazyM
+    , foldChars
+    , head
+    , last
+    , null
+    , length
+    , any
+    , all
+    , maximum
+    , minimum
+    , find
+    , index
+
+    -- * Primitive Character Parsers
+    , nextChar
+    , drawChar
+    , unDrawChar
+    , peekChar
+    , isEndOfChars
+
+    -- * Parsing Lenses
+    , splitAt
+    , span
+    , break
+    , groupBy
+    , group
+    , word
+    , line
+
+    -- * Transforming Text and Character Streams
+    , drop
+    , dropWhile
+    , pack
+    , unpack
+    , intersperse
+
+    -- * FreeT Transformations
+    , chunksOf
+    , splitsWith
+    , splits
+    , groupsBy
+    , groups
+    , lines
+    , unlines
+    , words
+    , unwords
+    , intercalate
 
     -- * Re-exports
     -- $reexports
-    module Data.Text,
-    module Pipes.Parse
+    , module Data.ByteString
+    , module Data.Text
+    , module Pipes.Parse
+    , module Pipes.Group
     ) where
 
-import Control.Exception (throwIO, try)
-import Control.Monad (liftM, unless)
-import Control.Monad.Trans.State.Strict (StateT(..))
+import Control.Applicative ((<*))
+import Control.Monad (liftM, join)
+import Control.Monad.Trans.State.Strict (StateT(..), modify)
 import qualified Data.Text as T
-import qualified Data.Text.IO as T
-import qualified Data.Text.Encoding as TE
-import qualified Data.Text.Encoding.Error as TE
 import Data.Text (Text)
 import qualified Data.Text.Lazy as TL
-import qualified Data.Text.Lazy.IO as TL
-import Data.Text.Lazy.Internal (foldrChunks, defaultChunkSize)
-import Data.ByteString.Unsafe (unsafeTake, unsafeDrop)
 import Data.ByteString (ByteString)
-import qualified Data.ByteString as B
-import Data.Char (ord, isSpace)
+import Data.Functor.Constant (Constant(Constant, getConstant))
 import Data.Functor.Identity (Identity)
-import qualified Data.List as List
-import Foreign.C.Error (Errno(Errno), ePIPE)
-import qualified GHC.IO.Exception as G
+
 import Pipes
-import qualified Pipes.ByteString as PB
-import qualified Pipes.ByteString.Parse as PBP
-import qualified Pipes.Text.Internal as PE
-import Pipes.Text.Parse (
-    nextChar, drawChar, unDrawChar, peekChar, isEndOfChars )
-import Pipes.Core (respond, Server')
+import Pipes.Group (folds, maps, concats, intercalates, FreeT(..), FreeF(..))
+import qualified Pipes.Group as PG
 import qualified Pipes.Parse as PP
-import Pipes.Parse (input, concat, FreeT)
-import qualified Pipes.Safe.Prelude as Safe
-import qualified Pipes.Safe as Safe
-import Pipes.Safe (MonadSafe(..), Base(..))
+import Pipes.Parse (Parser)
 import qualified Pipes.Prelude as P
-import qualified System.IO as IO
 import Data.Char (isSpace)
 import Data.Word (Word8)
+import Foreign.Storable (sizeOf)
+import Data.Bits (shiftL)
 import Prelude hiding (
     all,
     any,
@@ -202,203 +128,47 @@ import Prelude hiding (
     words,
     writeFile )
 
--- | Convert a lazy 'TL.Text' into a 'Producer' of strict 'Text's
-fromLazy :: (Monad m) => TL.Text -> Producer' Text m ()
-fromLazy  = foldrChunks (\e a -> yield e >> a) (return ()) 
-{-# INLINABLE fromLazy #-}
-
--- | Stream text from 'stdin'
-stdin :: MonadIO m => Producer Text m (Producer ByteString m ())
-stdin = fromHandle IO.stdin
-{-# INLINABLE stdin #-}
-
-{-| Convert a 'IO.Handle' into a text stream using a text size 
-    determined by the good sense of the text library. 
--}
-
-fromHandle :: MonadIO m => IO.Handle -> Producer Text m (Producer ByteString m ())
-fromHandle h = decodeUtf8 (PB.fromHandle h)
-{-# INLINE fromHandle#-}
-
-{-| Stream text from a file using Pipes.Safe
-
->>> runSafeT $ runEffect $ Text.readFile "hello.hs" >-> Text.map toUpper >-> hoist lift Text.stdout
-MAIN = PUTSTRLN "HELLO WORLD"
--}
-
-readFile :: (MonadSafe m) => FilePath -> Producer Text m (Producer ByteString m ())
-readFile file = Safe.withFile file IO.ReadMode fromHandle
-{-# INLINABLE readFile #-}
-
-{-| Stream lines of text from stdin (for testing in ghci etc.) 
-
->>> let safely = runSafeT . runEffect
->>> safely $ for Text.stdinLn (lift . lift . print . T.length)
-hello
-5
-world
-5
-
--}
-stdinLn :: MonadIO m => Producer' Text m ()
-stdinLn = go where
-    go = do
-        eof <- liftIO (IO.hIsEOF IO.stdin)
-        unless eof $ do
-            txt <- liftIO (T.hGetLine IO.stdin)
-            yield txt
-            go
-
-
-{-| Stream text to 'stdout'
-
-    Unlike 'toHandle', 'stdout' gracefully terminates on a broken output pipe.
-
-    Note: For best performance, use @(for source (liftIO . putStr))@ instead of
-    @(source >-> stdout)@ in suitable cases.
--}
-stdout :: MonadIO m => Consumer' Text m ()
-stdout = go
-  where
-    go = do
-        txt <- await
-        x  <- liftIO $ try (T.putStr txt)
-        case x of
-            Left (G.IOError { G.ioe_type  = G.ResourceVanished
-                            , G.ioe_errno = Just ioe })
-                 | Errno ioe == ePIPE
-                     -> return ()
-            Left  e  -> liftIO (throwIO e)
-            Right () -> go
-{-# INLINABLE stdout #-}
-
-stdoutLn :: (MonadIO m) => Consumer' Text m ()
-stdoutLn = go
-  where
-    go = do
-        str <- await
-        x   <- liftIO $ try (T.putStrLn str)
-        case x of
-           Left (G.IOError { G.ioe_type  = G.ResourceVanished
-                           , G.ioe_errno = Just ioe })
-                | Errno ioe == ePIPE
-                    -> return ()
-           Left  e  -> liftIO (throwIO e)
-           Right () -> go
-{-# INLINABLE stdoutLn #-}
-
-{-| Convert a text stream into a 'Handle'
-
-    Note: again, for best performance, where possible use 
-    @(for source (liftIO . hPutStr handle))@ instead of @(source >-> toHandle handle)@.
--}
-toHandle :: MonadIO m => IO.Handle -> Consumer' Text m r
-toHandle h = for cat (liftIO . T.hPutStr h)
-{-# INLINABLE toHandle #-}
-
-{-# RULES "p >-> toHandle h" forall p h .
-        p >-> toHandle h = for p (\txt -> liftIO (T.hPutStr h txt))
-  #-}
+-- $setup
+-- >>> :set -XOverloadedStrings
+-- >>> import Data.Text (Text)
+-- >>> import qualified Data.Text as T
+-- >>> import qualified Data.Text.Lazy.IO as TL
+-- >>> import Data.Char
 
+-- | Convert a lazy 'TL.Text' into a 'Producer' of strict 'Text's. Producers in 
+-- IO can be found in 'Pipes.Text.IO' or in pipes-bytestring, employed with the
+-- decoding lenses in 'Pipes.Text.Encoding'
+fromLazy :: (Monad m) => TL.Text -> Producer' Text m ()
+fromLazy  = TL.foldrChunks (\e a -> yield e >> a) (return ())
+{-# INLINE fromLazy #-}
 
--- | Stream text into a file. Uses @pipes-safe@.
-writeFile :: (MonadSafe m) => FilePath -> Consumer' Text m ()
-writeFile file = Safe.withFile file IO.WriteMode toHandle
+(^.) :: a -> ((b -> Constant b b) -> (a -> Constant b a)) -> b
+a ^. lens = getConstant (lens Constant a)
 
 -- | Apply a transformation to each 'Char' in the stream
+
+-- >>> let margaret =  ["Margaret, are you grieving\nOver Golde","ngrove unleaving?":: Text]
+-- >>> TL.putStrLn . toLazy $ each margaret >-> map Data.Char.toUpper
+-- MARGARET, ARE YOU GRIEVING
+-- OVER GOLDENGROVE UNLEAVING?
 map :: (Monad m) => (Char -> Char) -> Pipe Text Text m r
 map f = P.map (T.map f)
 {-# INLINABLE map #-}
 
-{-# RULES "p >-> map f" forall p f .
-        p >-> map f = for p (\txt -> yield (T.map f txt))
-  #-}
-
 -- | Map a function over the characters of a text stream and concatenate the results
+
 concatMap
     :: (Monad m) => (Char -> Text) -> Pipe Text Text m r
 concatMap f = P.map (T.concatMap f)
 {-# INLINABLE concatMap #-}
 
-{-# RULES "p >-> concatMap f" forall p f .
-        p >-> concatMap f = for p (\txt -> yield (T.concatMap f txt))
-  #-}
-
--- | Transform a Pipe of 'Text' into a Pipe of 'ByteString's using UTF-8
--- encoding; @encodeUtf8 = Pipes.Prelude.map TE.encodeUtf8@ so more complex
--- encoding pipes can easily be constructed with the functions in @Data.Text.Encoding@
-encodeUtf8 :: Monad m => Pipe Text ByteString m r
-encodeUtf8 = P.map TE.encodeUtf8
-{-# INLINEABLE encodeUtf8 #-}
-
-{-# RULES "p >-> encodeUtf8" forall p .
-        p >-> encodeUtf8 = for p (\txt -> yield (TE.encodeUtf8 txt))
-  #-}
-
--- | Transform a Pipe of 'String's into one of 'Text' chunks
-pack :: Monad m => Pipe String Text m r
-pack = P.map T.pack
-{-# INLINEABLE pack #-}
-
-{-# RULES "p >-> pack" forall p .
-        p >-> pack = for p (\txt -> yield (T.pack txt))
-  #-}
-
--- | Transform a Pipes of 'Text' chunks into one of 'String's
-unpack :: Monad m => Pipe Text String m r
-unpack = for cat (\t -> yield (T.unpack t))
-{-# INLINEABLE unpack #-}
-
-{-# RULES "p >-> unpack" forall p .
-        p >-> unpack = for p (\txt -> yield (T.unpack txt))
-  #-}
-
--- | @toCaseFold@, @toLower@, @toUpper@ and @stripStart@ are standard 'Text' utility, 
--- here acting on a 'Text' pipe, rather as they would  on a lazy text
-toCaseFold :: Monad m => Pipe Text Text m ()
-toCaseFold = P.map T.toCaseFold
-{-# INLINEABLE toCaseFold #-}
-
-{-# RULES "p >-> toCaseFold" forall p .
-        p >-> toCaseFold = for p (\txt -> yield (T.toCaseFold txt))
-  #-}
-
-
--- | lowercase incoming 'Text'
-toLower :: Monad m => Pipe Text Text m ()
-toLower = P.map T.toLower
-{-# INLINEABLE toLower #-}
-
-{-# RULES "p >-> toLower" forall p .
-        p >-> toLower = for p (\txt -> yield (T.toLower txt))
-  #-}
-
--- | uppercase incoming 'Text'
-toUpper :: Monad m => Pipe Text Text m ()
-toUpper = P.map T.toUpper
-{-# INLINEABLE toUpper #-}
-
-{-# RULES "p >-> toUpper" forall p .
-        p >-> toUpper = for p (\txt -> yield (T.toUpper txt))
-  #-}
-
--- | Remove leading white space from an incoming succession of 'Text's 
-stripStart :: Monad m => Pipe Text Text m r
-stripStart = do
-    chunk <- await
-    let text = T.stripStart chunk
-    if T.null text
-      then stripStart
-      else cat
-{-# INLINEABLE stripStart #-}
-
--- | @(take n)@ only allows @n@ individual characters to pass; 
+-- | @(take n)@ only allows @n@ individual characters to pass;
 --  contrast @Pipes.Prelude.take@ which would let @n@ chunks pass.
 take :: (Monad m, Integral a) => a -> Pipe Text Text m ()
 take n0 = go n0 where
     go n
         | n <= 0    = return ()
-        | otherwise = do
+        | otherwise = do 
             txt <- await
             let len = fromIntegral (T.length txt)
             if (len > n)
@@ -408,21 +178,6 @@ take n0 = go n0 where
                     go (n - len)
 {-# INLINABLE take #-}
 
--- | @(drop n)@ drops the first @n@ characters
-drop :: (Monad m, Integral a) => a -> Pipe Text Text m r
-drop n0 = go n0 where
-    go n
-        | n <= 0    = cat
-        | otherwise = do
-            txt <- await
-            let len = fromIntegral (T.length txt)
-            if (len >= n)
-                then do
-                    yield (T.drop (fromIntegral n) txt)
-                    cat
-                else go (n - len)
-{-# INLINABLE drop #-}
-
 -- | Take characters until they fail the predicate
 takeWhile :: (Monad m) => (Char -> Bool) -> Pipe Text Text m ()
 takeWhile predicate = go
@@ -437,41 +192,59 @@ takeWhile predicate = go
             else yield prefix
 {-# INLINABLE takeWhile #-}
 
--- | Drop characters until they fail the predicate
-dropWhile :: (Monad m) => (Char -> Bool) -> Pipe Text Text m r
-dropWhile predicate = go where
-    go = do
-        txt <- await
-        case T.findIndex (not . predicate) txt of
-            Nothing -> go
-            Just i -> do
-                yield (T.drop i txt)
-                cat
-{-# INLINABLE dropWhile #-}
-
 -- | Only allows 'Char's to pass if they satisfy the predicate
 filter :: (Monad m) => (Char -> Bool) -> Pipe Text Text m r
 filter predicate = P.map (T.filter predicate)
 {-# INLINABLE filter #-}
 
-{-# RULES "p >-> filter q" forall p q .
-        p >-> filter q = for p (\txt -> yield (T.filter q txt))
-  #-}
-  
 -- | Strict left scan over the characters
+-- >>> let margaret = ["Margaret, are you grieving\nOver Golde","ngrove unleaving?":: Text]
+-- >>> let title_caser a x = case a of ' ' -> Data.Char.toUpper x; _ -> x
+-- >>> toLazy $ each margaret >-> scan title_caser ' ' 
+-- " Margaret, Are You Grieving\nOver Goldengrove Unleaving?"
+
 scan
     :: (Monad m)
     => (Char -> Char -> Char) -> Char -> Pipe Text Text m r
-scan step begin = go begin
+scan step begin = do
+    yield (T.singleton begin)
+    go begin
   where
     go c = do
         txt <- await
         let txt' = T.scanl step c txt
             c' = T.last txt'
-        yield txt'
+        yield (T.tail txt')
         go c'
 {-# INLINABLE scan #-}
 
+-- | @toCaseFold@, @toLower@, @toUpper@ and @stripStart@ are standard 'Text' utilities,
+-- here acting as 'Text' pipes, rather as they would  on a lazy text
+toCaseFold :: Monad m => Pipe Text Text m r
+toCaseFold = P.map T.toCaseFold
+{-# INLINEABLE toCaseFold #-}
+
+-- | lowercase incoming 'Text'
+toLower :: Monad m => Pipe Text Text m r
+toLower = P.map T.toLower
+{-# INLINEABLE toLower #-}
+
+-- | uppercase incoming 'Text'
+toUpper :: Monad m => Pipe Text Text m r
+toUpper = P.map T.toUpper
+{-# INLINEABLE toUpper #-}
+
+-- | Remove leading white space from an incoming succession of 'Text's
+stripStart :: Monad m => Pipe Text Text m r
+stripStart = do
+    chunk <- await
+    let text = T.stripStart chunk
+    if T.null text
+      then stripStart
+      else do yield text
+              cat
+{-# INLINEABLE stripStart #-}
+
 {-| Fold a pure 'Producer' of strict 'Text's into a lazy
     'TL.Text'
 -}
@@ -491,11 +264,12 @@ toLazyM = liftM TL.fromChunks . P.toListM
 {-# INLINABLE toLazyM #-}
 
 -- | Reduce the text stream using a strict left fold over characters
-fold
+foldChars
     :: Monad m
     => (x -> Char -> x) -> x -> (x -> r) -> Producer Text m () -> m r
-fold step begin done = P.fold (T.foldl' step) begin done
-{-# INLINABLE fold #-}
+foldChars step begin done = P.fold (T.foldl' step) begin done
+{-# INLINABLE foldChars #-}
+
 
 -- | Retrieve the first 'Char'
 head :: (Monad m) => Producer Text m () -> m (Maybe Char)
@@ -577,37 +351,95 @@ find predicate p = head (p >-> filter predicate)
 index
     :: (Monad m, Integral a)
     => a-> Producer Text m () -> m (Maybe Char)
-index n p = head (p >-> drop n)
+index n p = head (drop n p)
 {-# INLINABLE index #-}
 
 
--- | Store a tally of how many segments match the given 'Text'
-count :: (Monad m, Num n) => Text -> Producer Text m () -> m n
-count c p = P.fold (+) 0 id (p >-> P.map (fromIntegral . T.count c))
-{-# INLINABLE count #-}
 
--- | Transform a Pipe of 'ByteString's expected to be UTF-8 encoded
--- into a Pipe of Text
+-- | Consume the first character from a stream of 'Text'
+--
+-- 'next' either fails with a 'Left' if the 'Producer' has no more characters or
+-- succeeds with a 'Right' providing the next character and the remainder of the
+-- 'Producer'.
 
-decodeUtf8 :: Monad m => Producer ByteString m r -> Producer Text m (Producer ByteString m r)
-decodeUtf8 = go PE.streamDecodeUtf8 where
-  go dec0 p = do 
-     x <- lift (next p)
-     case x of Left r -> return (return r)
-               Right (chunk, p') -> 
-                 case dec0 chunk of PE.Some text _ dec -> do yield text
-                                                             go dec p'
-                                    PE.Other text bs -> do yield text
-                                                           return (do yield bs
-                                                                      p')
+nextChar
+    :: (Monad m)
+    => Producer Text m r
+    -> m (Either r (Char, Producer Text m r))
+nextChar = go
+  where
+    go p = do
+        x <- next p
+        case x of
+            Left   r       -> return (Left r)
+            Right (txt, p') -> case (T.uncons txt) of
+                Nothing        -> go p'
+                Just (c, txt') -> return (Right (c, yield txt' >> p'))
+{-# INLINABLE nextChar #-}
+
+-- | Draw one 'Char' from a stream of 'Text', returning 'Left' if the 'Producer' is empty
+
+drawChar :: (Monad m) => Parser Text m (Maybe Char)
+drawChar = do
+    x <- PP.draw
+    case x of
+        Nothing  -> return Nothing
+        Just txt -> case (T.uncons txt) of
+            Nothing        -> drawChar
+            Just (c, txt') -> do
+                PP.unDraw txt'
+                return (Just c)
+{-# INLINABLE drawChar #-}
+
+-- | Push back a 'Char' onto the underlying 'Producer'
+unDrawChar :: (Monad m) => Char -> Parser Text m ()
+unDrawChar c = modify (yield (T.singleton c) >>)
+{-# INLINABLE unDrawChar #-}
+
+{-| 'peekChar' checks the first 'Char' in the stream, but uses 'unDrawChar' to
+    push the 'Char' back
+
+> peekChar = do
+>     x <- drawChar
+>     case x of
+>         Left  _  -> return ()
+>         Right c -> unDrawChar c
+>     return x
+
+-}
+
+peekChar :: (Monad m) => Parser Text m (Maybe Char)
+peekChar = do
+    x <- drawChar
+    case x of
+        Nothing  -> return ()
+        Just c -> unDrawChar c
+    return x
+{-# INLINABLE peekChar #-}
+
+{-| Check if the underlying 'Producer' has no more characters
+
+    Note that this will skip over empty 'Text' chunks, unlike
+    'PP.isEndOfInput' from @pipes-parse@, which would consider
+    an empty 'Text' a valid bit of input.
+
+> isEndOfChars = liftM isLeft peekChar
+-}
+isEndOfChars :: (Monad m) => Parser Text m Bool
+isEndOfChars = do
+    x <- peekChar
+    return (case x of
+        Nothing -> True
+        Just _-> False )
+{-# INLINABLE isEndOfChars #-}
 
 -- | Splits a 'Producer' after the given number of characters
 splitAt
     :: (Monad m, Integral n)
     => n
-    -> Producer Text m r
-    -> Producer' Text m (Producer Text m r)
-splitAt = go
+    -> Lens' (Producer Text m r)
+             (Producer Text m (Producer Text m r))
+splitAt n0 k p0 = fmap join (k (go n0 p0))
   where
     go 0 p = return p
     go n p = do
@@ -626,30 +458,17 @@ splitAt = go
                         return (yield suffix >> p')
 {-# INLINABLE splitAt #-}
 
--- | Split a text stream into 'FreeT'-delimited text streams of fixed size
-chunksOf
-    :: (Monad m, Integral n)
-    => n -> Producer Text m r -> FreeT (Producer Text m) m r
-chunksOf n p0 = PP.FreeT (go p0)
-  where
-    go p = do
-        x <- next p
-        return $ case x of
-            Left   r       -> PP.Pure r
-            Right (txt, p') -> PP.Free $ do
-                p'' <- splitAt n (yield txt >> p')
-                return $ PP.FreeT (go p'')
-{-# INLINABLE chunksOf #-}
 
-{-| Split a text stream in two, where the first text stream is the longest
-    consecutive group of text that satisfy the predicate
--}
+-- | Split a text stream in two, producing the longest
+--   consecutive group of characters that satisfies the predicate
+--   and returning the rest
+
 span
     :: (Monad m)
     => (Char -> Bool)
-    -> Producer Text m r
-    -> Producer' Text m (Producer Text m r)
-span predicate = go
+    -> Lens' (Producer Text m r)
+             (Producer Text m (Producer Text m r))
+span predicate k p0 = fmap join (k (go p0))
   where
     go p = do
         x <- lift (next p)
@@ -666,123 +485,79 @@ span predicate = go
                         return (yield suffix >> p')
 {-# INLINABLE span #-}
 
-{-| Split a text stream in two, where the first text stream is the longest
+{-| Split a text stream in two, producing the longest
     consecutive group of characters that don't satisfy the predicate
 -}
 break
     :: (Monad m)
     => (Char -> Bool)
-    -> Producer Text m r
-    -> Producer Text m (Producer Text m r)
+    -> Lens' (Producer Text m r)
+             (Producer Text m (Producer Text m r))
 break predicate = span (not . predicate)
 {-# INLINABLE break #-}
 
-{-| Split a text stream into sub-streams delimited by characters that satisfy the
-    predicate
--}
-splitWith
-    :: (Monad m)
-    => (Char -> Bool)
-    -> Producer Text m r
-    -> PP.FreeT (Producer Text m) m r
-splitWith predicate p0 = PP.FreeT (go0 p0)
-  where
-    go0 p = do
-        x <- next p
-        case x of
-            Left   r       -> return (PP.Pure r)
-            Right (txt, p') ->
-                if (T.null txt)
-                then go0 p'
-                else return $ PP.Free $ do
-                    p'' <- span (not . predicate) (yield txt >> p')
-                    return $ PP.FreeT (go1 p'')
-    go1 p = do
-        x <- nextChar p
-        return $ case x of
-            Left   r      -> PP.Pure r
-            Right (_, p') -> PP.Free $ do
-                    p'' <- span (not . predicate) p'
-                    return $ PP.FreeT (go1 p'')
-{-# INLINABLE splitWith #-}
-
--- | Split a text stream using the given 'Char' as the delimiter
-split :: (Monad m)
-      => Char
-      -> Producer Text m r
-      -> FreeT (Producer Text m) m r
-split c = splitWith (c ==)
-{-# INLINABLE split #-}
-
-{-| Group a text stream into 'FreeT'-delimited text streams using the supplied
-    equality predicate
+{-| Improper lens that splits after the first group of equivalent Chars, as
+    defined by the given equivalence relation
 -}
 groupBy
     :: (Monad m)
     => (Char -> Char -> Bool)
-    -> Producer Text m r
-    -> FreeT (Producer Text m) m r
-groupBy equal p0 = PP.FreeT (go p0)
-  where
+    -> Lens' (Producer Text m r)
+             (Producer Text m (Producer Text m r))
+groupBy equals k p0 = fmap join (k ((go p0))) where
     go p = do
-        x <- next p
+        x <- lift (next p)
         case x of
-            Left   r       -> return (PP.Pure r)
-            Right (txt, p') -> case (T.uncons txt) of
+            Left   r       -> return (return r)
+            Right (txt, p') -> case T.uncons txt of
                 Nothing      -> go p'
-                Just (c, _) -> do
-                    return $ PP.Free $ do
-                        p'' <- span (equal c) (yield txt >> p')
-                        return $ PP.FreeT (go p'')
+                Just (c, _) -> (yield txt >> p') ^. span (equals c)
 {-# INLINABLE groupBy #-}
 
--- | Group a text stream into 'FreeT'-delimited text streams of identical characters
-group
-    :: (Monad m) => Producer Text m r -> FreeT (Producer Text m) m r
+-- | Improper lens that splits after the first succession of identical 'Char' s
+group :: Monad m
+      => Lens' (Producer Text m r)
+               (Producer Text m (Producer Text m r))
 group = groupBy (==)
 {-# INLINABLE group #-}
 
-{-| Split a text stream into 'FreeT'-delimited lines
+{-| Improper lens that splits a 'Producer' after the first word
+
+    Unlike 'words', this does not drop leading whitespace
 -}
-lines
-    :: (Monad m) => Producer Text m r -> FreeT (Producer Text m) m r
-lines p0 = PP.FreeT (go0 p0)
+word :: (Monad m)
+     => Lens' (Producer Text m r)
+              (Producer Text m (Producer Text m r))
+word k p0 = fmap join (k (to p0))
   where
-    go0 p = do
-        x <- next p
-        case x of
-            Left   r       -> return (PP.Pure r)
-            Right (txt, p') ->
-                if (T.null txt)
-                then go0 p'
-                else return $ PP.Free $ go1 (yield txt >> p')
-    go1 p = do
-        p' <- break ('\n' ==) p
-        return $ PP.FreeT $ do
-            x  <- nextChar p'
-            case x of
-                Left   r      -> return $ PP.Pure r
-                Right (_, p'') -> go0 p''
-{-# INLINABLE lines #-}
-
+    to p = do
+        p' <- p^.span isSpace
+        p'^.break isSpace
+{-# INLINABLE word #-}
 
+line :: (Monad m)
+     => Lens' (Producer Text m r)
+              (Producer Text m (Producer Text m r))
+line = break (== '\n')
+{-# INLINABLE line #-}
 
--- | Split a text stream into 'FreeT'-delimited words
-words
-    :: (Monad m) => Producer Text m r -> FreeT (Producer Text m) m r
-words = go
-  where
-    go p = PP.FreeT $ do
-        x <- next (p >-> dropWhile isSpace)
-        return $ case x of
-            Left   r       -> PP.Pure r
-            Right (bs, p') -> PP.Free $ do
-                p'' <- break isSpace (yield bs >> p')
-                return (go p'')
-{-# INLINABLE words #-}
+-- | @(drop n)@ drops the first @n@ characters
+drop :: (Monad m, Integral n)
+     => n -> Producer Text m r -> Producer Text m r
+drop n p = do
+    p' <- lift $ runEffect (for (p ^. splitAt n) discard)
+    p'
+{-# INLINABLE drop #-}
 
+-- | Drop characters until they fail the predicate
+dropWhile :: (Monad m)
+    => (Char -> Bool) -> Producer Text m r -> Producer Text m r
+dropWhile predicate p = do
+    p' <- lift $ runEffect (for (p ^. span predicate) discard)
+    p'
+{-# INLINABLE dropWhile #-}
 
--- | Intersperse a 'Char' in between the characters of the text stream
+-- | Intersperse a 'Char' in between the characters of stream of 'Text'
 intersperse
     :: (Monad m) => Char -> Producer Text m r -> Producer Text m r
 intersperse c = go0
@@ -804,65 +579,215 @@ intersperse c = go0
                 go1 p'
 {-# INLINABLE intersperse #-}
 
+
+-- | Improper lens from unpacked 'Word8's to packaged 'ByteString's
+pack :: Monad m => Lens' (Producer Char m r) (Producer Text m r)
+pack k p = fmap _unpack (k (_pack p))
+{-# INLINABLE pack #-}
+
+-- | Improper lens from packed 'ByteString's to unpacked 'Word8's
+unpack :: Monad m => Lens' (Producer Text m r) (Producer Char m r)
+unpack k p = fmap _pack (k (_unpack p))
+{-# INLINABLE unpack #-}
+
+_pack :: Monad m => Producer Char m r -> Producer Text m r
+_pack p = folds step id done (p^.PG.chunksOf defaultChunkSize)
+  where
+    step diffAs w8 = diffAs . (w8:)
+
+    done diffAs = T.pack (diffAs [])
+{-# INLINABLE _pack #-}
+
+_unpack :: Monad m => Producer Text m r -> Producer Char m r
+_unpack p = for p (each . T.unpack)
+{-# INLINABLE _unpack #-}
+
+defaultChunkSize :: Int
+defaultChunkSize = 16384 - (sizeOf (undefined :: Int) `shiftL` 1)
+
+
+-- | Split a text stream into 'FreeT'-delimited text streams of fixed size
+chunksOf
+    :: (Monad m, Integral n)
+    => n -> Lens' (Producer Text m r)
+                  (FreeT (Producer Text m) m r)
+chunksOf n k p0 = fmap concats (k (FreeT (go p0)))
+  where
+    go p = do
+        x <- next p
+        return $ case x of
+            Left   r       -> Pure r
+            Right (txt, p') -> Free $ do
+                p'' <- (yield txt >> p') ^. splitAt n
+                return $ FreeT (go p'')
+{-# INLINABLE chunksOf #-}
+
+
+{-| Split a text stream into sub-streams delimited by characters that satisfy the
+    predicate
+-}
+splitsWith
+    :: (Monad m)
+    => (Char -> Bool)
+    -> Producer Text m r -> FreeT (Producer Text m) m r
+splitsWith predicate p0 = FreeT (go0 p0)
+  where
+    go0 p = do
+        x <- next p
+        case x of
+            Left   r       -> return (Pure r)
+            Right (txt, p') ->
+                if (T.null txt)
+                then go0 p'
+                else return $ Free $ do
+                    p'' <-  (yield txt >> p') ^. span (not . predicate)
+                    return $ FreeT (go1 p'')
+    go1 p = do
+        x <- nextChar p
+        return $ case x of
+            Left   r      -> Pure r
+            Right (_, p') -> Free $ do
+                    p'' <- p' ^. span (not . predicate)
+                    return $ FreeT (go1 p'')
+{-# INLINABLE splitsWith #-}
+
+-- | Split a text stream using the given 'Char' as the delimiter
+splits :: (Monad m)
+      => Char
+      -> Lens' (Producer Text m r)
+               (FreeT (Producer Text m) m r)
+splits c k p =
+          fmap (intercalates (yield (T.singleton c))) (k (splitsWith (c ==) p))
+{-# INLINABLE splits #-}
+
+{-| Isomorphism between a stream of 'Text' and groups of equivalent 'Char's , using the
+    given equivalence relation
+-}
+groupsBy
+    :: Monad m
+    => (Char -> Char -> Bool)
+    -> Lens' (Producer Text m x) (FreeT (Producer Text m) m x)
+groupsBy equals k p0 = fmap concats (k (FreeT (go p0))) where
+  go p = do x <- next p
+            case x of Left   r       -> return (Pure r)
+                      Right (bs, p') -> case T.uncons bs of
+                             Nothing      -> go p'
+                             Just (c, _) -> do return $ Free $ do
+                                                 p'' <- (yield bs >> p')^.span (equals c)
+                                                 return $ FreeT (go p'')
+{-# INLINABLE groupsBy #-}
+
+
+-- | Like 'groupsBy', where the equality predicate is ('==')
+groups
+    :: Monad m
+    => Lens' (Producer Text m x) (FreeT (Producer Text m) m x)
+groups = groupsBy (==)
+{-# INLINABLE groups #-}
+
+
+
+{-| Split a text stream into 'FreeT'-delimited lines
+-}
+lines
+    :: (Monad m) => Lens' (Producer Text m r)  (FreeT (Producer Text m) m r)
+lines k p = fmap _unlines (k (_lines p))
+{-# INLINABLE lines #-}
+
+unlines
+    :: Monad m
+    => Lens' (FreeT (Producer Text m) m r) (Producer Text m r)
+unlines k p = fmap _lines (k (_unlines p))
+{-# INLINABLE unlines #-}
+
+_lines :: Monad m
+             => Producer Text m r -> FreeT (Producer Text m) m r
+_lines p0 = FreeT (go0 p0)
+    where
+      go0 p = do
+              x <- next p
+              case x of
+                  Left   r       -> return (Pure r)
+                  Right (txt, p') ->
+                      if (T.null txt)
+                      then go0 p'
+                      else return $ Free $ go1 (yield txt >> p')
+      go1 p = do
+              p' <- p ^. break ('\n' ==)
+              return $ FreeT $ do
+                  x  <- nextChar p'
+                  case x of
+                      Left   r      -> return $ Pure r
+                      Right (_, p'') -> go0 p''
+{-# INLINABLE _lines #-}
+
+_unlines :: Monad m
+         => FreeT (Producer Text m) m r -> Producer Text m r
+_unlines = concats . maps (<* yield (T.singleton '\n'))
+{-# INLINABLE _unlines #-}
+
+-- | Split a text stream into 'FreeT'-delimited words. Note that 
+-- roundtripping with e.g. @over words id@ eliminates extra space
+-- characters as with @Prelude.unwords . Prelude.words@
+words
+    :: (Monad m) => Lens' (Producer Text m r) (FreeT (Producer Text m) m r)
+words k p = fmap _unwords (k (_words p))
+{-# INLINABLE words #-}
+
+unwords
+    :: Monad m
+    => Lens' (FreeT (Producer Text m) m r) (Producer Text m r)
+unwords k p = fmap _words (k (_unwords p))
+{-# INLINABLE unwords #-}
+
+_words :: (Monad m) => Producer Text m r -> FreeT (Producer Text m) m r
+_words p = FreeT $ do
+        x <- next (dropWhile isSpace p)
+        return $ case x of
+            Left   r       -> Pure r
+            Right (bs, p') -> Free $ do
+                p'' <-  (yield bs >> p') ^. break isSpace
+                return (_words p'')
+{-# INLINABLE _words #-}
+
+_unwords :: (Monad m) => FreeT (Producer Text m) m r -> Producer Text m r
+_unwords = intercalates (yield $ T.singleton ' ')
+{-# INLINABLE _unwords #-}
+
+
 {-| 'intercalate' concatenates the 'FreeT'-delimited text streams after
     interspersing a text stream in between them
 -}
 intercalate
     :: (Monad m)
-    => Producer Text m ()
-    -> FreeT (Producer Text m) m r
-    -> Producer Text m r
+    => Producer Text m () -> FreeT (Producer Text m) m r -> Producer Text m r
 intercalate p0 = go0
   where
     go0 f = do
-        x <- lift (PP.runFreeT f)
+        x <- lift (runFreeT f)
         case x of
-            PP.Pure r -> return r
-            PP.Free p -> do
+            Pure r -> return r
+            Free p -> do
                 f' <- p
                 go1 f'
     go1 f = do
-        x <- lift (PP.runFreeT f)
+        x <- lift (runFreeT f)
         case x of
-            PP.Pure r -> return r
-            PP.Free p -> do
+            Pure r -> return r
+            Free p -> do
                 p0
                 f' <- p
                 go1 f'
 {-# INLINABLE intercalate #-}
 
-{-| Join 'FreeT'-delimited lines into a text stream
--}
-unlines
-    :: (Monad m) => FreeT (Producer Text m) m r -> Producer Text m r
-unlines = go
-  where
-    go f = do
-        x <- lift (PP.runFreeT f)
-        case x of
-            PP.Pure r -> return r
-            PP.Free p -> do
-                f' <- p
-                yield $ T.singleton '\n'
-                go f'
-{-# INLINABLE unlines #-}
-
-{-| Join 'FreeT'-delimited words into a text stream
--}
-unwords
-    :: (Monad m) => FreeT (Producer Text m) m r -> Producer Text m r
-unwords = intercalate (yield $ T.pack " ")
-{-# INLINABLE unwords #-}
 
-{- $parse
-    The following parsing utilities are single-character analogs of the ones found
-    @pipes-parse@.
--}
 
 {- $reexports
-    @Pipes.Text.Parse@ re-exports 'nextChar', 'drawChar', 'unDrawChar', 'peekChar', and 'isEndOfChars'.
-    
+
     @Data.Text@ re-exports the 'Text' type.
 
-    @Pipes.Parse@ re-exports 'input', 'concat', and 'FreeT' (the type).
--}
\ No newline at end of file
+    @Pipes.Parse@ re-exports 'input', 'concat', 'FreeT' (the type) and the 'Parse' synonym.
+-}
+
+
+type Lens' a b = forall f . Functor f => (b -> f b) -> (a -> f a)