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.

O(1) The empty ByteString

O(1) Convert a Char into a ByteString

O(n) Convert a String into a ByteString.

O(n) Converts a ByteString to a String.

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

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

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

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

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.

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

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

This is a partial function, consider using unsnoc instead.

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.

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.

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 packed string, reduces the packed string 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

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

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

maximum returns the maximum value from a ByteString

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

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 empty 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).

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

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

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

Since: 0.11.2.0

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

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: 0.11.2.0

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

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: 0.11.2.0

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

breakEnd behaves like break but from the end of the ByteString

breakEnd p == spanEnd (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 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.

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

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

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

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

Since: 0.11.4.0

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

Since: 0.11.4.0

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

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

tokens isSpace = words

unlines joins lines, appending a terminating newline after each.

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

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

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. This implementation uses memchr(3).

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.

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

Since: 0.10.12.0

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

O(1) 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 (by memchr) to the query element, or Nothing if there is no such element.

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: 0.11.1.0

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

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: 0.11.1.0

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
count '\n' == length . lines

But more efficiently than using length on the intermediate list.

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 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 chars into a pair of ByteStrings. Note that this performs two pack operations.

Since: 0.11.1.0

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.

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

>>> 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

A variant of readInt specialised to Int64.

A variant of readInt specialised to Int32.

A variant of readInt specialised to Int16.

A variant of readInt specialised to Int8.

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

>>> 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

A variant of readWord specialised to Word64.

A variant of readWord specialised to Word32.

A variant of readWord specialised to Word16.

A variant of readWord specialised to Word8.

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

>>> 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 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

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

getContents. Equivalent to hGetContents stdin. Will read lazily

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.

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.

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 in between, and hence hPut alone is not 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

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.