| bytestring-0.9.0.1: Fast, packed, strict and lazy byte arrays with a list interface | Contents | Index

Data.ByteString.Lazy.Char8 |

Portability | non-portable (imports Data.ByteString.Lazy)
Stability | experimental
Maintainer | dons@cse.unsw.edu.au

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
Synopsis

data ByteString
empty :: ByteString
singleton :: Char -> ByteString
pack :: [Char] -> ByteString
unpack :: ByteString -> [Char]
fromChunks :: [ByteString] -> ByteString
toChunks :: ByteString -> [ByteString]
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 :: ByteString -> ByteString
init :: 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
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
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString
repeat :: Char -> ByteString
replicate :: Int64 -> Char -> ByteString
cycle :: ByteString -> ByteString
iterate :: (Char -> Char) -> Char -> ByteString
unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
take :: Int64 -> ByteString -> ByteString
drop :: Int64 -> ByteString -> ByteString
splitAt :: Int64 -> ByteString -> (ByteString, ByteString)
takeWhile :: (Char -> Bool) -> ByteString -> ByteString
dropWhile :: (Char -> Bool) -> ByteString -> ByteString
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
group :: ByteString -> [ByteString]
groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
inits :: ByteString -> [ByteString]
tails :: ByteString -> [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
elem :: Char -> ByteString -> Bool
notElem :: Char -> ByteString -> Bool
find :: (Char -> Bool) -> ByteString -> Maybe Char
filter :: (Char -> Bool) -> ByteString -> ByteString
index :: ByteString -> Int64 -> Char
elemIndex :: Char -> ByteString -> Maybe Int64
elemIndices :: Char -> ByteString -> [Int64]
findIndex :: (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]
copy :: ByteString -> ByteString
readInt :: ByteString -> Maybe (Int, ByteString)
readInteger :: ByteString -> Maybe (Integer, 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 ()

The `ByteString` type
data ByteString

A space-efficient representation of a Word8 vector, supporting many efficient operations. A `ByteString` contains 8-bit characters only. Instances of Eq, Ord, Read, Show, Data, Typeable
Instances

Data ByteString
Eq ByteString
Monoid ByteString
Ord ByteString
Read ByteString
Show ByteString
Typeable ByteString

Introducing and eliminating `ByteString`s
empty :: ByteString
O(1) The empty `ByteString`
singleton :: Char -> ByteString
O(1) Convert a Char into a `ByteString`
pack :: [Char] -> ByteString
O(n) Convert a String into a `ByteString`.
unpack :: ByteString -> [Char]
O(n) Converts a `ByteString` to a String.
fromChunks :: [ByteString] -> ByteString
O(c) Convert a list of strict `ByteString` into a lazy `ByteString`
toChunks :: ByteString -> [ByteString]
O(n) Convert a lazy `ByteString` into a list of strict `ByteString`
Basic interface
cons :: Char -> ByteString -> ByteString
O(1) `cons` is analogous to '(:)' for lists.
cons' :: Char -> ByteString -> ByteString
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
O(n) Append a Char to the end of a `ByteString`. Similar to `cons`, this function performs a memcpy.
append :: ByteString -> ByteString -> ByteString
O(n/c) Append two ByteStrings
head :: ByteString -> Char
O(1) Extract the first element of a ByteString, which must be non-empty.
uncons :: ByteString -> Maybe (Char, ByteString)
O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.
last :: ByteString -> Char
O(1) Extract the last element of a packed string, which must be non-empty.
tail :: ByteString -> ByteString
O(1) Extract the elements after the head of a ByteString, which must be non-empty.
init :: ByteString -> ByteString
O(n/c) Return all the elements of a `ByteString` except the last one.
null :: ByteString -> Bool
O(1) Test whether a ByteString is empty.
length :: ByteString -> Int64
O(n/c) `length` returns the length of a ByteString as an Int64
Transforming ByteStrings
map :: (Char -> Char) -> ByteString -> ByteString
O(n) `map` `f xs` is the ByteString obtained by applying `f` to each element of `xs`
reverse :: ByteString -> ByteString
O(n) `reverse` `xs` returns the elements of `xs` in reverse order.
intersperse :: Char -> ByteString -> ByteString
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
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]
The `transpose` function transposes the rows and columns of its `ByteString` argument.
Reducing `ByteString`s (folds)
foldl :: (a -> Char -> a) -> a -> ByteString -> a
`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
`foldl` is like foldl, but strict in the accumulator.
foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
`foldl1` is a variant of `foldl` that has no starting value argument, and thus must be applied to non-empty ByteStrings.
foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
`foldl1` is like `foldl1`, but strict in the accumulator.
foldr :: (Char -> a -> a) -> a -> ByteString -> a
`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.
foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
`foldr1` is a variant of `foldr` that has no starting value argument, and thus must be applied to non-empty `ByteString`s
Special folds
concat :: [ByteString] -> ByteString
O(n) Concatenate a list of ByteStrings.
concatMap :: (Char -> ByteString) -> ByteString -> ByteString
Map a function over a `ByteString` and concatenate the results
any :: (Char -> Bool) -> ByteString -> Bool
Applied to a predicate and a ByteString, `any` determines if any element of the `ByteString` satisfies the predicate.
all :: (Char -> Bool) -> ByteString -> Bool
Applied to a predicate and a `ByteString`, `all` determines if all elements of the `ByteString` satisfy the predicate.
maximum :: ByteString -> Char
`maximum` returns the maximum value from a `ByteString`
minimum :: ByteString -> Char
`minimum` returns the minimum value from a `ByteString`
Building ByteStrings
Scans
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
`scanl` is similar to `foldl`, but returns a list of successive reduced values from the left. This function will fuse.
     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.
Accumulating maps
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
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.
mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString
O(n) map Char functions, provided with the index at each position
Infinite ByteStrings
repeat :: Char -> ByteString
``repeat` x` is an infinite ByteString, with `x` the value of every element.
replicate :: Int64 -> Char -> ByteString
O(n) ``replicate` n x` is a ByteString of length `n` with `x` the value of every element.
cycle :: ByteString -> ByteString
`cycle` ties a finite ByteString into a circular one, or equivalently, the infinite repetition of the original ByteString.
iterate :: (Char -> Char) -> Char -> ByteString
``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
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
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`.
drop :: Int64 -> ByteString -> ByteString
O(n/c) `drop` `n xs` returns the suffix of `xs` after the first `n` elements, or `[]` if `n > `length` xs`.
splitAt :: Int64 -> ByteString -> (ByteString, ByteString)
O(n/c) `splitAt` `n xs` is equivalent to `(`take` n xs, `drop` n xs)`.
takeWhile :: (Char -> Bool) -> ByteString -> ByteString
`takeWhile`, applied to a predicate `p` and a ByteString `xs`, returns the longest prefix (possibly empty) of `xs` of elements that satisfy `p`.
dropWhile :: (Char -> Bool) -> ByteString -> ByteString
`dropWhile` `p xs` returns the suffix remaining after `takeWhile` `p xs`.
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
`span` `p xs` breaks the ByteString into two segments. It is equivalent to `(`takeWhile` p xs, `dropWhile` p xs)`
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
`break` `p` is equivalent to ``span` (not . p)`.
group :: ByteString -> [ByteString]
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 sublist 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]
The `groupBy` function is the non-overloaded version of `group`.
inits :: ByteString -> [ByteString]
O(n) Return all initial segments of the given `ByteString`, shortest first.
tails :: ByteString -> [ByteString]
O(n) Return all final segments of the given `ByteString`, longest first.
Breaking into many substrings
split :: Char -> ByteString -> [ByteString]
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"          == ["",""]
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 ByteStrings that are slices of the original.
splitWith :: (Char -> Bool) -> ByteString -> [ByteString]
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",""]
Breaking into lines and words
lines :: ByteString -> [ByteString]
`lines` breaks a ByteString up into a list of ByteStrings at newline Chars. The resulting strings do not contain newlines.
words :: ByteString -> [ByteString]
`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
`unlines` is an inverse operation to `lines`. It joins lines, after appending a terminating newline to each.
unwords :: [ByteString] -> ByteString
The `unwords` function is analogous to the `unlines` function, on words.
Predicates
isPrefixOf :: ByteString -> ByteString -> Bool
O(n) The `isPrefixOf` function takes two ByteStrings and returns True iff the first is a prefix of the second.
Searching ByteStrings
Searching by equality
elem :: Char -> ByteString -> Bool
O(n) `elem` is the `ByteString` membership predicate. This implementation uses `memchr(3)`.
notElem :: Char -> ByteString -> Bool
O(n) `notElem` is the inverse of `elem`
Searching with a predicate
find :: (Char -> Bool) -> ByteString -> Maybe Char
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
O(n) `filter`, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.
Indexing ByteStrings
index :: ByteString -> Int64 -> Char
O(1) `ByteString` index (subscript) operator, starting from 0.
elemIndex :: Char -> ByteString -> Maybe Int64
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.
elemIndices :: Char -> ByteString -> [Int64]
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
The `findIndex` function takes a predicate and a `ByteString` and returns the index of the first element in the ByteString satisfying the predicate.
findIndices :: (Char -> Bool) -> ByteString -> [Int64]
The `findIndices` function extends `findIndex`, by returning the indices of all elements satisfying the predicate, in ascending order.
count :: Char -> ByteString -> Int64
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)]
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]
`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.
Ordered ByteStrings
Low level conversions
Copying ByteStrings
copy :: ByteString -> ByteString
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
readInt :: ByteString -> Maybe (Int, ByteString)
readInt reads an Int 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 int read, and the rest of the string.
readInteger :: ByteString -> Maybe (Integer, ByteString)
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 int read, and the rest of the string.
I/O with `ByteString`s
Standard input and output
getContents :: IO ByteString
getContents. Equivalent to hGetContents stdin. Will read lazily
putStr :: ByteString -> IO ()
Write a ByteString to stdout
putStrLn :: ByteString -> IO ()
Write a ByteString to stdout, appending a newline byte
interact :: (ByteString -> ByteString) -> IO ()
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. It's great for writing one line programs!
Files
readFile :: FilePath -> IO ByteString
Read an entire file lazily into a `ByteString`. Use 'text mode' on Windows to interpret newlines
writeFile :: FilePath -> ByteString -> IO ()
Write a `ByteString` to a file.
appendFile :: FilePath -> ByteString -> IO ()
Append a `ByteString` to a file.
I/O with Handles
hGetContents :: Handle -> IO ByteString
Read entire handle contents lazily into a `ByteString`. Chunks are read on demand, using the default chunk size.
hGet :: Handle -> Int -> IO ByteString
Read `n` bytes into a `ByteString`, directly from the specified Handle.
hGetNonBlocking :: Handle -> Int -> IO ByteString
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.
hPut :: Handle -> ByteString -> IO ()
Outputs a `ByteString` to the specified Handle.
Produced by Haddock version 0.8