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

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

Type synonym for the lazy flavour of ByteString.

Since: 0.11.2.0

O(1) The empty ByteString

O(1) Convert a Word8 into a ByteString

O(n) Convert a '[Word8]' into a ByteString.

O(n) Converts a ByteString to a '[Word8]'.

O(1) Convert a strict ByteString into a lazy ByteString.

O(n) Convert a lazy ByteString into a strict ByteString.

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

O(c) Convert a list of strict ByteString into a lazy ByteString

O(c) Convert a lazy ByteString into a list of strict ByteString

Consume the chunks of a lazy ByteString with a natural right fold.

Consume the chunks of a lazy ByteString with a strict, tail-recursive, accumulating left fold.

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

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.

O(n/c) Append a byte to the end of a ByteString

O(n/c) Append two ByteStrings

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

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

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

• It is no faster than using init and last

O(n/c) Extract the last element of a ByteString, which must be finite and non-empty.

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

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

O(1) Test whether a ByteString is empty.

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

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

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

The intersperse function takes a Word8 and a ByteString and `intersperses' that byte between the elements of the ByteString. It is analogous to the intersperse function on Lists.

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

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

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' is like foldl, but strict in the accumulator.

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

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

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

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

Since: 0.11.2.0

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

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

Since: 0.11.2.0

O(n) Concatenate a list of ByteStrings.

Map a function over a ByteString and concatenate the results

O(n) Applied to a predicate and a ByteString, any determines if any element of the ByteString satisfies the predicate.

O(n) Applied to a predicate and a ByteString, all determines if all elements of the ByteString satisfy the predicate.

O(n) maximum returns the maximum value from a ByteString

O(n) minimum returns the minimum value from a ByteString

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

Since: 0.11.1.0

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

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

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

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

Since: 0.11.2.0

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: 0.11.2.0

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

Since: 0.11.2.0

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.

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.

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

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

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

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

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

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.

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.

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: 0.11.2.0

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

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: 0.11.2.0

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

Similar to takeWhile, returns the longest (possibly empty) prefix of elements satisfying the predicate.

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

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

>>> {-# LANGUAGE OverloadedLists #-)
>>> takeWhileEnd even [1,2,3,4,6]
[4,6]

Since: 0.11.2.0

Similar to dropWhile, drops the longest (possibly empty) prefix of elements satisfying the predicate and returns the remainder.

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.

>>> {-# LANGUAGE OverloadedLists #-)
>>> dropWhileEnd even [1,2,3,4,6]
[1,2,3]

Since: 0.11.2.0

Similar to span, returns the longest (possibly empty) prefix of elements satisfying the predicate and the remainder of the string.

span p is equivalent to break (not . p) and to (takeWhile p &&& dropWhile p).

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

spanEnd p is equivalent to breakEnd (not . p) and to (takeWhileEnd p &&& dropWhileEnd p).

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: 0.11.2.0

Similar to break, returns the longest (possibly empty) prefix of elements which do not satisfy the predicate and the remainder of the string.

break p is equivalent to span (not . p) and to (takeWhile (not . p) &&& dropWhile (not . p)).

Returns the longest (possibly empty) suffix of elements which do not satisfy the predicate and the remainder of the string.

breakEnd p is equivalent to spanEnd (not . p) and to (takeWhileEnd (not . p) &&& dropWhileEnd (not . p)).

Since: 0.11.2.0

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.

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

O(n) Return all initial segments of the given ByteString, shortest first.

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

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: 0.10.8.0

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.

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

split 10  "a\nb\nd\ne" == ["a","b","d","e"]   -- fromEnum '\n' == 10
split 97  "aXaXaXa"    == ["","X","X","X",""] -- fromEnum 'a' == 97
split 120 "x"          == ["",""]             -- fromEnum 'x' == 120
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 ByteStrings that are slices of the original.

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 (==97) "aabbaca" == ["","","bb","c",""] -- fromEnum 'a' == 97
splitWith undefined ""     == []                  -- and not [""]

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

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

O(n) elem is the ByteString membership predicate.

O(n) notElem is the inverse of elem

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.

find f p = case findIndex f p of Just n -> Just (p ! n) ; _ -> Nothing

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

O(n) The partition function takes a predicate a ByteString and returns the pair of ByteStrings with elements which do and do not satisfy the predicate, respectively; i.e.,

partition p bs == (filter p xs, filter (not . p) xs)

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

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

0 <= n < length bs

Since: 0.11.0.0

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

0 <= n < length bs

Since: 0.11.0.0

O(n) The elemIndex function returns the index of the first element in the given ByteString which is equal to the query element, or Nothing if there is no such element. This implementation uses memchr(3).

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: 0.10.6.0

O(n) The elemIndices function extends elemIndex, by returning the indices of all elements equal to the query element, in ascending order. This implementation uses memchr(3).

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

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

Since: 0.10.12.0

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

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

count = length . elemIndices

But more efficiently than using length on the intermediate list.

O(n) zip takes two ByteStrings and returns a list of corresponding pairs of bytes. If one input ByteString is short, excess elements of the longer ByteString are discarded. This is equivalent to a pair of unpack operations.

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.

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

Since: 0.11.1.0

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

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.

getContents. Equivalent to hGetContents stdin. Will read lazily

Write a ByteString to stdout

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.

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.

Write a ByteString to a file.

Append a ByteString to a file.

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.

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

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.

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

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.

A synonym for hPut, for compatibility