bytestring-0.12.2.0: Fast, compact, strict and lazy byte strings with a list interface

Copyright | (c) Don Stewart 2006-2008 (c) Duncan Coutts 2006-2011
License | BSD-style
Maintainer | dons00@gmail.com, duncan@community.haskell.org
Stability | stable
Portability | portable
Safe Haskell | Trustworthy
Language | Haskell2010

Data.ByteString.Lazy.Char8

Contents

- The `ByteString` type
- Introducing and eliminating `ByteString`s
- Basic interface
- Transforming ByteStrings
- Reducing `ByteString`s (folds)
  - Special folds
- Building ByteStrings
  - Scans
  - Accumulating maps
  - Infinite ByteStrings
  - Unfolding ByteStrings
- Substrings
  - Breaking strings
  - Breaking into many substrings
  - Breaking into lines and words
- Predicates
- Searching ByteStrings
  - Searching by equality
  - Searching with a predicate
- Indexing ByteStrings
- Zipping and unzipping ByteStrings
- Ordered ByteStrings
- Low level conversions
  - Copying ByteStrings
- Reading from ByteStrings
- I/O with `ByteString`s
  - Standard input and output
  - Files
  - I/O with Handles

Description

Manipulate lazy `ByteString`s using `Char` operations. All Chars will be truncated to 8 bits. It can be expected that these functions will run at identical speeds to their `Word8` equivalents in Data.ByteString.Lazy.

This module is intended to be imported `qualified`, to avoid name clashes with Prelude functions. eg.

    import qualified Data.ByteString.Lazy.Char8 as C

The Char8 interface to bytestrings provides an instance of IsString for the ByteString type, enabling you to use string literals, and have them implicitly packed to ByteStrings. Use `{-# LANGUAGE OverloadedStrings #-}` to enable this.

Synopsis

- data ByteString
- empty :: ByteString
- singleton :: Char -> ByteString
- pack :: [Char] -> ByteString
- unpack :: ByteString -> [Char]
- fromChunks :: [StrictByteString] -> LazyByteString
- toChunks :: LazyByteString -> [StrictByteString]
- fromStrict :: StrictByteString -> LazyByteString
- toStrict :: LazyByteString -> StrictByteString
- cons :: Char -> ByteString -> ByteString
- cons' :: Char -> ByteString -> ByteString
- snoc :: ByteString -> Char -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: ByteString -> Char
- uncons :: ByteString -> Maybe (Char, ByteString)
- last :: ByteString -> Char
- tail :: HasCallStack => ByteString -> ByteString
- unsnoc :: ByteString -> Maybe (ByteString, Char)
- init :: HasCallStack => ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int64
- map :: (Char -> Char) -> ByteString -> ByteString
- reverse :: ByteString -> ByteString
- intersperse :: Char -> ByteString -> ByteString
- intercalate :: ByteString -> [ByteString] -> ByteString
- transpose :: [ByteString] -> [ByteString]
- foldl :: (a -> Char -> a) -> a -> ByteString -> a
- foldl' :: (a -> Char -> a) -> a -> ByteString -> a
- foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
- foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
- foldr :: (Char -> a -> a) -> a -> ByteString -> a
- foldr' :: (Char -> a -> a) -> a -> ByteString -> a
- foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
- foldr1' :: (Char -> Char -> Char) -> ByteString -> Char
- concat :: [ByteString] -> ByteString
- concatMap :: (Char -> ByteString) -> ByteString -> ByteString
- any :: (Char -> Bool) -> ByteString -> Bool
- all :: (Char -> Bool) -> ByteString -> Bool
- maximum :: ByteString -> Char
- minimum :: ByteString -> Char
- compareLength :: ByteString -> Int64 -> Ordering
- scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
- scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString
- scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
- scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
- mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- repeat :: Char -> ByteString
- replicate :: Int64 -> Char -> ByteString
- cycle :: HasCallStack => ByteString -> ByteString
- iterate :: (Char -> Char) -> Char -> ByteString
- unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
- take :: Int64 -> ByteString -> ByteString
- takeEnd :: Int64 -> ByteString -> ByteString
- drop :: Int64 -> ByteString -> ByteString
- dropEnd :: Int64 -> ByteString -> ByteString
- splitAt :: Int64 -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Char -> Bool) -> ByteString -> ByteString
- takeWhileEnd :: (Char -> Bool) -> ByteString -> ByteString
- dropWhile :: (Char -> Bool) -> ByteString -> ByteString
- dropWhileEnd :: (Char -> Bool) -> ByteString -> ByteString
- span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: ByteString -> [ByteString]
- initsNE :: ByteString -> NonEmpty ByteString
- tailsNE :: ByteString -> NonEmpty ByteString
- stripPrefix :: ByteString -> ByteString -> Maybe ByteString
- stripSuffix :: ByteString -> ByteString -> Maybe ByteString
- split :: Char -> ByteString -> [ByteString]
- splitWith :: (Char -> Bool) -> ByteString -> [ByteString]
- lines :: ByteString -> [ByteString]
- words :: ByteString -> [ByteString]
- unlines :: [ByteString] -> ByteString
- unwords :: [ByteString] -> ByteString
- isPrefixOf :: ByteString -> ByteString -> Bool
- isSuffixOf :: ByteString -> ByteString -> Bool
- elem :: Char -> ByteString -> Bool
- notElem :: Char -> ByteString -> Bool
- find :: (Char -> Bool) -> ByteString -> Maybe Char
- filter :: (Char -> Bool) -> ByteString -> ByteString
- partition :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- index :: ByteString -> Int64 -> Char
- indexMaybe :: ByteString -> Int64 -> Maybe Char
- (!?) :: ByteString -> Int64 -> Maybe Char
- elemIndex :: Char -> ByteString -> Maybe Int64
- elemIndexEnd :: Char -> ByteString -> Maybe Int64
- elemIndices :: Char -> ByteString -> [Int64]
- findIndex :: (Char -> Bool) -> ByteString -> Maybe Int64
- findIndexEnd :: (Char -> Bool) -> ByteString -> Maybe Int64
- findIndices :: (Char -> Bool) -> ByteString -> [Int64]
- count :: Char -> ByteString -> Int64
- zip :: ByteString -> ByteString -> [(Char, Char)]
- zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
- packZipWith :: (Char -> Char -> Char) -> ByteString -> ByteString -> ByteString
- unzip :: [(Char, Char)] -> (ByteString, ByteString)
- copy :: ByteString -> ByteString
- readInt :: ByteString -> Maybe (Int, ByteString)
- readInt64 :: ByteString -> Maybe (Int64, ByteString)
- readInt32 :: ByteString -> Maybe (Int32, ByteString)
- readInt16 :: ByteString -> Maybe (Int16, ByteString)
- readInt8 :: ByteString -> Maybe (Int8, ByteString)
- readWord :: ByteString -> Maybe (Word, ByteString)
- readWord64 :: ByteString -> Maybe (Word64, ByteString)
- readWord32 :: ByteString -> Maybe (Word32, ByteString)
- readWord16 :: ByteString -> Maybe (Word16, ByteString)
- readWord8 :: ByteString -> Maybe (Word8, ByteString)
- readInteger :: ByteString -> Maybe (Integer, ByteString)
- readNatural :: ByteString -> Maybe (Natural, ByteString)
- getContents :: IO ByteString
- putStr :: ByteString -> IO ()
- putStrLn :: ByteString -> IO ()
- interact :: (ByteString -> ByteString) -> IO ()
- readFile :: FilePath -> IO ByteString
- writeFile :: FilePath -> ByteString -> IO ()
- appendFile :: FilePath -> ByteString -> IO ()
- hGetContents :: Handle -> IO ByteString
- hGet :: Handle -> Int -> IO ByteString
- hGetNonBlocking :: Handle -> Int -> IO ByteString
- hPut :: Handle -> ByteString -> IO ()
- hPutNonBlocking :: Handle -> ByteString -> IO ByteString
- hPutStr :: Handle -> ByteString -> IO ()
- hPutStrLn :: Handle -> ByteString -> IO ()

# The `ByteString` type

data ByteString Source #

A space-efficient representation of a `Word8` vector, supporting many efficient operations.

A `LazyByteString` contains 8-bit bytes, or by using the operations from Data.ByteString.Lazy.Char8 it can be interpreted as containing 8-bit characters.

#### Instances

Instances details

NFData ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods rnf :: ByteString -> () Source #
Monoid ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods mempty :: ByteString # mappend :: ByteString -> ByteString -> ByteString # mconcat :: [ByteString] -> ByteString #
Semigroup ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods (<>) :: ByteString -> ByteString -> ByteString # sconcat :: NonEmpty ByteString -> ByteString # stimes :: Integral b => b -> ByteString -> ByteString #
Data ByteString Source # |

Instance details

Defined in Data.ByteString.Lazy.Internal

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ByteString -> c ByteString #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c ByteString #

toConstr :: ByteString -> Constr #

dataTypeOf :: ByteString -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c ByteString) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c ByteString) #

gmapT :: (forall b. Data b => b -> b) -> ByteString -> ByteString #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ByteString -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ByteString -> r #

gmapQ :: (forall d. Data d => d -> u) -> ByteString -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> ByteString -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString #

IsString ByteString Source # | Beware: `fromString` truncates multi-byte characters to octets. e.g. "枯朶に烏のとまりけり秋の暮" becomes �6k�nh~�Q��n�
Instance details Defined in Data.ByteString.Lazy.Internal Methods fromString :: String -> ByteString #
IsList ByteString Source # | Since: bytestring-0.10.12.0

Instance details

Defined in Data.ByteString.Lazy.Internal

Associated Types

type Item ByteString |
Instance details Defined in Data.ByteString.Lazy.Internal type Item ByteString = Word8

Methods

fromList :: [Item ByteString] -> ByteString #

fromListN :: Int -> [Item ByteString] -> ByteString #

toList :: ByteString -> [Item ByteString] #

Read ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods readsPrec :: Int -> ReadS ByteString # readList :: ReadS [ByteString] # readPrec :: ReadPrec ByteString # readListPrec :: ReadPrec [ByteString] #
Show ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods showsPrec :: Int -> ByteString -> ShowS # show :: ByteString -> String # showList :: [ByteString] -> ShowS #
Eq ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods (==) :: ByteString -> ByteString -> Bool Source # (/=) :: ByteString -> ByteString -> Bool Source #
Ord ByteString Source # |

Instance details

Defined in Data.ByteString.Lazy.Internal

Methods

compare :: ByteString -> ByteString -> Ordering Source #

(<) :: ByteString -> ByteString -> Bool Source #

(<=) :: ByteString -> ByteString -> Bool Source #

(>) :: ByteString -> ByteString -> Bool Source #

(>=) :: ByteString -> ByteString -> Bool Source #

max :: ByteString -> ByteString -> ByteString Source #

min :: ByteString -> ByteString -> ByteString Source #

Lift ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal Methods lift :: Quote m => ByteString -> m Exp Source # liftTyped :: forall (m :: Type -> Type). Quote m => ByteString -> Code m ByteString Source #
type Item ByteString Source # |
Instance details Defined in Data.ByteString.Lazy.Internal type Item ByteString = Word8

# Introducing and eliminating `ByteString`s

empty :: ByteString Source #

O(1) The empty `ByteString`

singleton :: Char -> ByteString Source #

O(1) Convert a `Char` into a `ByteString`

pack :: [Char] -> ByteString Source #

O(n) Convert a `String` into a `ByteString`.

unpack :: ByteString -> [Char] Source #

O(n) Converts a `ByteString` to a `String`.

fromChunks :: [StrictByteString] -> LazyByteString Source #

O(c) Convert a list of `StrictByteString` into a `LazyByteString`

toChunks :: LazyByteString -> [StrictByteString] Source #

O(c) Convert a `LazyByteString` into a list of `StrictByteString`

fromStrict :: StrictByteString -> LazyByteString Source #

O(1) Convert a `StrictByteString` into a `LazyByteString`.

toStrict :: LazyByteString -> StrictByteString Source #

O(n) Convert a `LazyByteString` into a `StrictByteString`.

Note that this is an expensive operation that forces the whole `LazyByteString` into memory and then copies all the data. If possible, try to avoid converting back and forth between strict and lazy bytestrings.

# Basic interface

cons :: Char -> ByteString -> ByteString infixr 5 Source #

O(1) `cons` is analogous to `(:)` for lists.

cons' :: Char -> ByteString -> ByteString infixr 5 Source #

O(1) Unlike `cons`, `cons'` is strict in the ByteString that we are consing onto. More precisely, it forces the head and the first chunk. It does this because, for space efficiency, it may coalesce the new byte onto the first 'chunk' rather than starting a new 'chunk'.

So that means you can't use a lazy recursive contruction like this:

    let xs = cons' c xs in xs

You can however use `cons`, as well as `repeat` and `cycle`, to build infinite lazy ByteStrings.

snoc :: ByteString -> Char -> ByteString infixl 5 Source #

O(n) Append a Char to the end of a `ByteString`. Similar to `cons`, this function performs a memcpy.

append :: ByteString -> ByteString -> ByteString Source #

O(n/c) Append two ByteStrings

head :: ByteString -> Char Source #

O(1) Extract the first element of a ByteString, which must be non-empty.

uncons :: ByteString -> Maybe (Char, ByteString) Source #

O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.

last :: ByteString -> Char Source #

O(1) Extract the last element of a packed string, which must be non-empty.

tail :: HasCallStack => ByteString -> ByteString Source #

O(1) Extract the elements after the head of a ByteString, which must be non-empty.

This is a partial function, consider using `uncons` instead.

unsnoc :: ByteString -> Maybe (ByteString, Char) Source #

O(n/c) Extract the `init` and `last` of a ByteString, returning Nothing if it is empty.

init :: HasCallStack => ByteString -> ByteString Source #

O(n/c) Returns all the elements of a `ByteString` except the last one.

This is a partial function, consider using `unsnoc` instead.

null :: ByteString -> Bool Source #

O(1) Test whether a ByteString is empty.

length :: ByteString -> Int64 Source #

O(c) `length` returns the length of a ByteString as an `Int64`

# Transforming ByteStrings

map :: (Char -> Char) -> ByteString -> ByteString Source #

O(n) `map` `f xs` is the ByteString obtained by applying `f` to each element of `xs`

reverse :: ByteString -> ByteString Source #

O(n) `reverse` `xs` returns the elements of `xs` in reverse order.

intersperse :: Char -> ByteString -> ByteString Source #

O(n) The `intersperse` function takes a Char and a `ByteString` and `intersperses' that Char between the elements of the `ByteString`. It is analogous to the intersperse function on Lists.

intercalate :: ByteString -> [ByteString] -> ByteString Source #

O(n) The `intercalate` function takes a `ByteString` and a list of `ByteString`s and concatenates the list after interspersing the first argument between each element of the list.

transpose :: [ByteString] -> [ByteString] Source #

The `transpose` function transposes the rows and columns of its `ByteString` argument.

# Reducing `ByteString`s (folds)

foldl :: (a -> Char -> a) -> a -> ByteString -> a Source #

`foldl`, applied to a binary operator, a starting value (typically the left-identity of the operator), and a ByteString, reduces the ByteString using the binary operator, from left to right.

foldl' :: (a -> Char -> a) -> a -> ByteString -> a Source #

`foldl'` is like foldl, but strict in the accumulator.

foldl1 :: (Char -> Char -> Char) -> ByteString -> Char Source #

`foldl1` is a variant of `foldl` that has no starting value argument, and thus must be applied to non-empty `ByteString`s.

foldl1' :: (Char -> Char -> Char) -> ByteString -> Char Source #

`foldl1'` is like `foldl1`, but strict in the accumulator.

foldr :: (Char -> a -> a) -> a -> ByteString -> a Source #

`foldr`, applied to a binary operator, a starting value (typically the right-identity of the operator), and a packed string, reduces the packed string using the binary operator, from right to left.

foldr' :: (Char -> a -> a) -> a -> ByteString -> a Source #

`foldr'` is like `foldr`, but strict in the accumulator.

Since: bytestring-0.11.2.0

foldr1 :: (Char -> Char -> Char) -> ByteString -> Char Source #

`foldr1` is a variant of `foldr` that has no starting value argument, and thus must be applied to non-empty `ByteString`s

foldr1' :: (Char -> Char -> Char) -> ByteString -> Char Source #

`foldr1'` is like `foldr1`, but strict in the accumulator.

Since: bytestring-0.11.2.0

## Special folds

concat :: [ByteString] -> ByteString Source #

O(n) Concatenate a list of ByteStrings.

concatMap :: (Char -> ByteString) -> ByteString -> ByteString Source #

Map a function over a `ByteString` and concatenate the results

any :: (Char -> Bool) -> ByteString -> Bool Source #

Applied to a predicate and a ByteString, `any` determines if any element of the `ByteString` satisfies the predicate.

all :: (Char -> Bool) -> ByteString -> Bool Source #

Applied to a predicate and a `ByteString`, `all` determines if all elements of the `ByteString` satisfy the predicate.

maximum :: ByteString -> Char Source #

`maximum` returns the maximum value from a `ByteString`

minimum :: ByteString -> Char Source #

`minimum` returns the minimum value from a `ByteString`

compareLength :: ByteString -> Int64 -> Ordering Source #

O(c) `compareLength` compares the length of a `ByteString` to an `Int64`

Since: bytestring-0.11.1.0

# Building ByteStrings

## Scans

scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString Source #

`scanl` is similar to `foldl`, but returns a list of successive reduced values from the left.

    scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]

Note that

    last (scanl f z xs) == foldl f z xs.

scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString Source #

`scanl1` is a variant of `scanl` that has no starting value argument.

    scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]

Since: bytestring-0.11.2.0

scanr Source #

Arguments

:: (Char -> Char -> Char) | element -> accumulator -> new accumulator
-> Char | starting value of accumulator
-> ByteString | input of length n
-> ByteString | output of length n+1

`scanr` is similar to `foldr`, but returns a list of successive reduced values from the right.

    scanr f z [..., x{n-1}, xn] == [..., x{n-1} `f` (xn `f` z), xn `f` z, z]

Note that

    head (scanr f z xs) == foldr f z xs
    last (scanr f z xs) == z

Since: bytestring-0.11.2.0

scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString Source #

`scanr1` is a variant of `scanr` that has no starting value argument.

Since: bytestring-0.11.2.0

## Accumulating maps

mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) Source #

The `mapAccumL` function behaves like a combination of `map` and `foldl`; it applies a function to each element of a ByteString, passing an accumulating parameter from left to right, and returning a final value of this accumulator together with the new ByteString.

mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) Source #

The `mapAccumR` function behaves like a combination of `map` and `foldr`; it applies a function to each element of a ByteString, passing an accumulating parameter from right to left, and returning a final value of this accumulator together with the new ByteString.

## Infinite ByteStrings

repeat :: Char -> ByteString Source #

``repeat` x` is an infinite ByteString, with `x` the value of every element.

replicate :: Int64 -> Char -> ByteString Source #

O(n) ``replicate` n x` is a ByteString of length `n` with `x` the value of every element.

cycle :: HasCallStack => ByteString -> ByteString Source #

`cycle` ties a finite ByteString into a circular one, or equivalently, the infinite repetition of the original ByteString.

iterate :: (Char -> Char) -> Char -> ByteString Source #

``iterate` f x` returns an infinite ByteString of repeated applications of `f` to `x`:

    iterate f x == [x, f x, f (f x), ...]

## Unfolding ByteStrings

unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString Source #

O(n) The `unfoldr` function is analogous to the List 'unfoldr'. `unfoldr` builds a ByteString from a seed value. The function takes the element and returns `Nothing` if it is done producing the ByteString or returns `Just` `(a,b)`, in which case, `a` is a prepending to the ByteString and `b` is used as the next element in a recursive call.

# Substrings

## Breaking strings

take :: Int64 -> ByteString -> ByteString Source #

O(n/c) `take` `n`, applied to a ByteString `xs`, returns the prefix of `xs` of length `n`, or `xs` itself if `n > `length` xs`.

takeEnd :: Int64 -> ByteString -> ByteString Source #

O(c) ``takeEnd` n xs` is equivalent to ``drop` (`length` xs - n) xs`. Takes `n` elements from end of bytestring.

    >>> takeEnd 3 "abcdefg"
    "efg"
    >>> takeEnd 0 "abcdefg"
    ""
    >>> takeEnd 4 "abc"
    "abc"

Since: bytestring-0.11.2.0

drop :: Int64 -> ByteString -> ByteString Source #

O(n/c) `drop` `n xs` returns the suffix of `xs` after the first `n` elements, or `empty` if `n > `length` xs`.

dropEnd :: Int64 -> ByteString -> ByteString Source #

O(n) ``dropEnd` n xs` is equivalent to ``take` (`length` xs - n) xs`. Drops `n` elements from end of bytestring.

    >>> dropEnd 3 "abcdefg"
    "abcd"
    >>> dropEnd 0 "abcdefg"
    "abcdefg"
    >>> dropEnd 4 "abc"
    ""

Since: bytestring-0.11.2.0

splitAt :: Int64 -> ByteString -> (ByteString, ByteString) Source #

O(n/c) `splitAt` `n xs` is equivalent to `(`take` n xs, `drop` n xs)`.

takeWhile :: (Char -> Bool) -> ByteString -> ByteString Source #

`takeWhile`, applied to a predicate `p` and a ByteString `xs`, returns the longest prefix (possibly empty) of `xs` of elements that satisfy `p`.

takeWhileEnd :: (Char -> Bool) -> ByteString -> ByteString Source #

Returns the longest (possibly empty) suffix of elements satisfying the predicate.

``takeWhileEnd` p` is equivalent to ``reverse` . `takeWhile` p . `reverse``.

Since: bytestring-0.11.2.0

dropWhile :: (Char -> Bool) -> ByteString -> ByteString Source #

`dropWhile` `p xs` returns the suffix remaining after `takeWhile` `p xs`.

dropWhileEnd :: (Char -> Bool) -> ByteString -> ByteString Source #

Similar to `dropWhileEnd`, drops the longest (possibly empty) suffix of elements satisfying the predicate and returns the remainder.

``dropWhileEnd` p` is equivalent to ``reverse` . `dropWhile` p . `reverse``.

Since: bytestring-0.11.2.0

span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

`span` `p xs` breaks the ByteString into two segments. It is equivalent to `(`takeWhile` p xs, `dropWhile` p xs)`

spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

`spanEnd` behaves like `span` but from the end of the `ByteString`. We have

    spanEnd (not.isSpace) "x y z" == ("x y ","z")

and

    spanEnd (not . isSpace) ps
       ==
    let (x,y) = span (not.isSpace) (reverse ps) in (reverse y, reverse x)

Since: bytestring-0.11.2.0

break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

`break` `p` is equivalent to ``span` (`not` . p)`.

breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

`breakEnd` behaves like `break` but from the end of the `ByteString`

breakEnd p == spanEnd (not.p)

Since: bytestring-0.11.2.0

group :: ByteString -> [ByteString] Source #

The `group` function takes a ByteString and returns a list of ByteStrings such that the concatenation of the result is equal to the argument. Moreover, each string in the result contains only equal elements. For example,

    group "Mississippi" = ["M","i","ss","i","ss","i","pp","i"]

It is a special case of `groupBy`, which allows the programmer to supply their own equality test.

groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString] Source #

The `groupBy` function is the non-overloaded version of `group`.

inits :: ByteString -> [ByteString] Source #

Returns all initial segments of the given `ByteString`, shortest first.

tails :: ByteString -> [ByteString] Source #

O(n) Returns all final segments of the given `ByteString`, longest first.

initsNE :: ByteString -> NonEmpty ByteString Source #

Returns all initial segments of the given `ByteString`, shortest first.

Since: bytestring-0.11.4.0

tailsNE :: ByteString -> NonEmpty ByteString Source #

O(n) Returns all final segments of the given `ByteString`, longest first.

Since: bytestring-0.11.4.0

stripPrefix :: ByteString -> ByteString -> Maybe ByteString Source #

O(n) The `stripPrefix` function takes two ByteStrings and returns `Just` the remainder of the second iff the first is its prefix, and otherwise `Nothing`.

Since: bytestring-0.10.8.0

stripSuffix :: ByteString -> ByteString -> Maybe ByteString Source #

O(n) The `stripSuffix` function takes two ByteStrings and returns `Just` the remainder of the second iff the first is its suffix, and otherwise `Nothing`.

## Breaking into many substrings

split :: Char -> ByteString -> [ByteString] Source #

O(n) Break a `ByteString` into pieces separated by the byte argument, consuming the delimiter. I.e.

    split '\n' "a\nb\nd\ne" == ["a","b","d","e"]
    split 'a'  "aXaXaXa"    == ["","X","X","X"]
    split 'x'  "x"          == ["",""]
    split undefined ""      == []  -- and not [""]

and

    intercalate [c] . split c == id
    split == splitWith . (==)

As for all splitting functions in this library, this function does not copy the substrings, it just constructs new `ByteString`s that are slices of the original.

splitWith :: (Char -> Bool) -> ByteString -> [ByteString] Source #

O(n) Splits a `ByteString` into components delimited by separators, where the predicate returns True for a separator element. The resulting components do not contain the separators. Two adjacent separators result in an empty component in the output. eg.

    splitWith (=='a') "aabbaca" == ["","","bb","c",""]
    splitWith undefined ""      == []  -- and not [""]

## Breaking into lines and words

lines :: ByteString -> [ByteString] Source #

`lines` lazily splits a ByteString into a list of ByteStrings at newline Chars (`'\n'`). The resulting strings do not contain newlines. The first chunk of the result is only strict in the first chunk of the input.

Note that it does not regard CR (`'\r'`) as a newline character.

words :: ByteString -> [ByteString] Source #

`words` breaks a ByteString up into a list of words, which were delimited by Chars representing white space. And

    tokens isSpace = words

unlines :: [ByteString] -> ByteString Source #

`unlines` joins lines, appending a terminating newline after each.

Equivalent to ``concat` . Data.List.concatMap (\x -> [x, `singleton` '\n'])`.

unwords :: [ByteString] -> ByteString Source #

The `unwords` function is analogous to the `unlines` function, on words.

# Predicates

isPrefixOf :: ByteString -> ByteString -> Bool Source #

O(n) The `isPrefixOf` function takes two ByteStrings and returns `True` iff the first is a prefix of the second.

isSuffixOf :: ByteString -> ByteString -> Bool Source #

O(n) The `isSuffixOf` function takes two ByteStrings and returns `True` iff the first is a suffix of the second.

The following holds:

    isSuffixOf x y == reverse x `isPrefixOf` reverse y

# Searching ByteStrings

## Searching by equality

elem :: Char -> ByteString -> Bool Source #

O(n) `elem` is the `ByteString` membership predicate. This implementation uses `memchr(3)`.

notElem :: Char -> ByteString -> Bool Source #

O(n) `notElem` is the inverse of `elem`

## Searching with a predicate

find :: (Char -> Bool) -> ByteString -> Maybe Char Source #

O(n) The `find` function takes a predicate and a ByteString, and returns the first element in matching the predicate, or `Nothing` if there is no such element.

filter :: (Char -> Bool) -> ByteString -> ByteString Source #

O(n) `filter`, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.

partition :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

Since: bytestring-0.10.12.0

# Indexing ByteStrings

index :: ByteString -> Int64 -> Char Source #

O(1) `ByteString` index (subscript) operator, starting from 0.

indexMaybe :: ByteString -> Int64 -> Maybe Char Source #

O(1) `ByteString` index, starting from 0, that returns `Just` if:

    0 <= n < length bs

Since: bytestring-0.11.0.0

(!?) :: ByteString -> Int64 -> Maybe Char Source #

O(1) `ByteString` index, starting from 0, that returns `Just` if:

    0 <= n < length bs

Since: bytestring-0.11.0.0

elemIndex :: Char -> ByteString -> Maybe Int64 Source #

O(n) The `elemIndex` function returns the index of the first element in the given `ByteString` which is equal (by memchr) to the query element, or `Nothing` if there is no such element.

elemIndexEnd :: Char -> ByteString -> Maybe Int64 Source #

O(n) The `elemIndexEnd` function returns the last index of the element in the given `ByteString` which is equal to the query element, or `Nothing` if there is no such element. The following holds:

    elemIndexEnd c xs = case elemIndex c (reverse xs) of
      Nothing -> Nothing
      Just i  -> Just (length xs - 1 - i)

Since: bytestring-0.11.1.0

elemIndices :: Char -> ByteString -> [Int64] Source #

O(n) The `elemIndices` function extends `elemIndex`, by returning the indices of all elements equal to the query element, in ascending order.

findIndex :: (Char -> Bool) -> ByteString -> Maybe Int64 Source #

The `findIndex` function takes a predicate and a `ByteString` and returns the index of the first element in the ByteString satisfying the predicate.

findIndexEnd :: (Char -> Bool) -> ByteString -> Maybe Int64 Source #

The `findIndexEnd` function takes a predicate and a `ByteString` and returns the index of the last element in the ByteString satisfying the predicate.

Since: bytestring-0.11.1.0

findIndices :: (Char -> Bool) -> ByteString -> [Int64] Source #

The `findIndices` function extends `findIndex`, by returning the indices of all elements satisfying the predicate, in ascending order.

count :: Char -> ByteString -> Int64 Source #

count returns the number of times its argument appears in the ByteString

    count      == length . elemIndices
    count '\n' == length . lines

But more efficiently than using length on the intermediate list.

# Zipping and unzipping ByteStrings

zip :: ByteString -> ByteString -> [(Char, Char)] Source #

O(n) `zip` takes two ByteStrings and returns a list of corresponding pairs of Chars. If one input ByteString is short, excess elements of the longer ByteString are discarded. This is equivalent to a pair of `unpack` operations, and so space usage may be large for multi-megabyte ByteStrings

zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a] Source #

`zipWith` generalises `zip` by zipping with the function given as the first argument, instead of a tupling function. For example, ``zipWith` (+)` is applied to two ByteStrings to produce the list of corresponding sums.

packZipWith :: (Char -> Char -> Char) -> ByteString -> ByteString -> ByteString Source #

A specialised version of `zipWith` for the common case of a simultaneous map over two ByteStrings, to build a 3rd.

Since: bytestring-0.11.1.0

unzip :: [(Char, Char)] -> (ByteString, ByteString) Source #

O(n) `unzip` transforms a list of pairs of chars into a pair of ByteStrings. Note that this performs two `pack` operations.

Since: bytestring-0.11.1.0

# Ordered ByteStrings

# Low level conversions

## Copying ByteStrings

copy :: ByteString -> ByteString Source #

O(n) Make a copy of the `ByteString` with its own storage. This is mainly useful to allow the rest of the data pointed to by the `ByteString` to be garbage collected, for example if a large string has been read in, and only a small part of it is needed in the rest of the program.

# Reading from ByteStrings

Note that a lazy `ByteString` may hold an unbounded stream of `'0'` digits, in which case the functions below may never return. If that's a concern, you can use `take` to first truncate the input to an acceptable length. Non-termination is also possible when reading arbitrary precision numbers via `readInteger` or `readNatural`, if the input is an unbounded stream of arbitrary decimal digits.

readInt :: ByteString -> Maybe (Int, ByteString) Source #

Try to read a signed `Int` value from the `ByteString`, returning `Just (val, str)` on success, where `val` is the value read and `str` is the rest of the input string. If the sequence of digits decodes to a value larger than can be represented by an `Int`, the returned value will be `Nothing`.

`readInt` does not ignore leading whitespace, the value must start immediately at the beginning of the input string.

#### Examples

Expand

    >>> readInt "-1729 sum of cubes"
    Just (-1729," sum of cubes")
    >>> readInt "+1: readInt also accepts a leading '+'"
    Just (1, ": readInt also accepts a leading '+'")
    >>> readInt "not a decimal number"
    Nothing
    >>> readInt "12345678901234567890 overflows maxBound"
    Nothing
    >>> readInt "-12345678901234567890 underflows minBound"
    Nothing

readInt64 :: ByteString -> Maybe (Int64, ByteString) Source #

A variant of `readInt` specialised to `Int64`.

readInt32 :: ByteString -> Maybe (Int32, ByteString) Source #

A variant of `readInt` specialised to `Int32`.

readInt16 :: ByteString -> Maybe (Int16, ByteString) Source #

A variant of `readInt` specialised to `Int16`.

readInt8 :: ByteString -> Maybe (Int8, ByteString) Source #

A variant of `readInt` specialised to `Int8`.

readWord :: ByteString -> Maybe (Word, ByteString) Source #

Try to read a `Word` value from the `ByteString`, returning `Just (val, str)` on success, where `val` is the value read and `str` is the rest of the input string. If the sequence of digits decodes to a value larger than can be represented by a `Word`, the returned value will be `Nothing`.

`readWord` does not ignore leading whitespace, the value must start with a decimal digit immediately at the beginning of the input string. Leading `+` signs are not accepted.

#### Examples

Expand

    >>> readWord "1729 sum of cubes"
    Just (1729," sum of cubes")
    >>> readWord "+1729 has an explicit sign"
    Nothing
    >>> readWord "not a decimal number"
    Nothing
    >>> readWord "98765432109876543210 overflows maxBound"
    Nothing

readWord64 :: ByteString -> Maybe (Word64, ByteString) Source #

A variant of `readWord` specialised to `Word64`.

readWord32 :: ByteString -> Maybe (Word32, ByteString) Source #

A variant of `readWord` specialised to `Word32`.

readWord16 :: ByteString -> Maybe (Word16, ByteString) Source #

A variant of `readWord` specialised to `Word16`.

readWord8 :: ByteString -> Maybe (Word8, ByteString) Source #

A variant of `readWord` specialised to `Word8`.

readInteger :: ByteString -> Maybe (Integer, ByteString) Source #

`readInteger` reads an `Integer` from the beginning of the `ByteString`. If there is no `Integer` at the beginning of the string, it returns `Nothing`, otherwise it just returns the `Integer` read, and the rest of the string.

`readInteger` does not ignore leading whitespace, the value must start immediately at the beginning of the input string.

#### Examples

Expand

    >>> readInteger "-000111222333444555666777888999 all done"
    Just (-111222333444555666777888999," all done")
    >>> readInteger "+1: readInteger also accepts a leading '+'"
    Just (1, ": readInteger also accepts a leading '+'")
    >>> readInteger "not a decimal number"
    Nothing

readNatural :: ByteString -> Maybe (Natural, ByteString) Source #

`readNatural` reads a `Natural` number from the beginning of the `ByteString`. If there is no `Natural` number at the beginning of the string, it returns `Nothing`, otherwise it just returns the number read, and the rest of the string.

`readNatural` does not ignore leading whitespace, the value must start with a decimal digit immediately at the beginning of the input string. Leading `+` signs are not accepted.

#### Examples

Expand

    >>> readNatural "000111222333444555666777888999 all done"
    Just (111222333444555666777888999," all done")
    >>> readNatural "+000111222333444555666777888999 explicit sign"
    Nothing
    >>> readNatural "not a decimal number"
    Nothing

# I/O with `ByteString`s

ByteString I/O uses binary mode, without any character decoding or newline conversion. The fact that it does not respect the Handle newline mode is considered a flaw and may be changed in a future version.

## Standard input and output

getContents :: IO ByteString Source #

getContents. Equivalent to hGetContents stdin. Will read lazily

putStr :: ByteString -> IO () Source #

Write a ByteString to `stdout`.

The chunks will be written one at a time. Other threads might write to the `stdout` in between, and hence `putStr` alone is not suitable for concurrent writes.

putStrLn :: ByteString -> IO () Source #

Write a ByteString to `stdout`, appending a newline byte.

The chunks will be written one at a time, followed by a newline. Other threads might write to the `stdout` in between, and hence `putStrLn` alone is not suitable for concurrent writes.

interact :: (ByteString -> ByteString) -> IO () Source #

The interact function takes a function of type `ByteString -> ByteString` as its argument. The entire input from the standard input device is passed to this function as its argument, and the resulting string is output on the standard output device.

## Files

readFile :: FilePath -> IO ByteString Source #

Read an entire file lazily into a `ByteString`.

The `Handle` will be held open until EOF is encountered.

Note that this function's implementation relies on `hGetContents`. The reader is advised to read its documentation.

writeFile :: FilePath -> ByteString -> IO () Source #

Write a `ByteString` to a file.

appendFile :: FilePath -> ByteString -> IO () Source #

Append a `ByteString` to a file.

## I/O with Handles

hGetContents :: Handle -> IO ByteString Source #

Read entire handle contents lazily into a `ByteString`. Chunks are read on demand, using the default chunk size.

File handles are closed on EOF if all the file is read, or through garbage collection otherwise.

hGet :: Handle -> Int -> IO ByteString Source #

Read `n` bytes into a `ByteString`, directly from the specified `Handle`.

hGetNonBlocking :: Handle -> Int -> IO ByteString Source #

hGetNonBlocking is similar to `hGet`, except that it will never block waiting for data to become available, instead it returns only whatever data is available. If there is no data available to be read, `hGetNonBlocking` returns `empty`.

Note: on Windows and with Haskell implementation other than GHC, this function does not work correctly; it behaves identically to `hGet`.

hPut :: Handle -> ByteString -> IO () Source #

Outputs a `ByteString` to the specified `Handle`.

The chunks will be written one at a time. Other threads might write to the `Handle` in between, and hence `hPut` alone is not suitable for concurrent writes.

hPutNonBlocking :: Handle -> ByteString -> IO ByteString Source #

Similar to `hPut` except that it will never block. Instead it returns any tail that did not get written. This tail may be `empty` in the case that the whole string was written, or the whole original string if nothing was written. Partial writes are also possible.

Note: on Windows and with Haskell implementation other than GHC, this function does not work correctly; it behaves identically to `hPut`.

hPutStr :: Handle -> ByteString -> IO () Source #

A synonym for `hPut`, for compatibility

hPutStrLn :: Handle -> ByteString -> IO () Source #

Write a ByteString to a handle, appending a newline byte.

The chunks will be written one at a time, followed by a newline. Other threads might write to the `Handle` in between, and hence `hPutStrLn` alone is not suitable for concurrent writes.