Safe Haskell	None
Language	Haskell2010

Types

data WindowsString Source

Commonly used windows string as wide character bytes.

data WindowsChar Source

String construction

encodeUtf :: MonadThrow m => String -> m WindowsString Source

Partial unicode friendly encoding.

This encodes as UTF16-LE (strictly), which is a pretty good guess.

Throws an EncodingException if encoding fails. If the input does not contain surrogate chars, you can use unsafeEncodeUtf.

unsafeEncodeUtf :: HasCallStack => String -> WindowsString Source

Unsafe unicode friendly encoding.

Like encodeUtf, except it crashes when the input contains surrogate chars. For sanitized input, this can be useful.

encodeWith Source

Encode a String with the specified encoding.

Note: We expect a "wide char" encoding (e.g. UCS-2 or UTF-16). Anything that works with Word16 boundaries. Picking an incompatible encoding may crash filepath operations.

encodeFS :: String -> IO WindowsString Source

This mimics the behavior of the base library when doing filesystem operations (usually filepaths), which does permissive UTF-16 encoding, where coding errors generate Chars in the surrogate range.

The reason this is in IO is because it unifies with the Posix counterpart, which does require IO. This is safe to unsafePerformIO/unsafeDupablePerformIO.

encodeLE :: String -> IO WindowsString Source

This mimics the behavior of the base library when doing string operations, which does permissive UTF-16 encoding, where coding errors generate Chars in the surrogate range.

The reason this is in IO is because it unifies with the Posix counterpart, which does require IO. This is safe to unsafePerformIO/unsafeDupablePerformIO.

fromString :: String -> WindowsString Source

Like 'encodeLE but not in IO.

encodeLE was designed to have a symmetric type signature on unix and windows, but morally the function has no IO effects on windows, so we provide this variant without breaking existing API.

On windows, encodeLE is equivalent to encodeFS.

This function does not exist on unix.

Since: os-string-2.0.6

fromBytes :: MonadThrow m => ByteString -> m WindowsString Source

Constructs a platform string from a ByteString.

This ensures valid UCS-2LE. Note that this doesn't expand Word8 to Word16 on windows, so you may get invalid UTF-16.

Throws EncodingException on invalid UCS-2LE (although unlikely).

pstr :: QuasiQuoter Source

QuasiQuote a WindowsString. This accepts Unicode characters and encodes as UTF-16LE on windows.

singleton :: WindowsChar -> WindowsString Source

empty :: WindowsString Source

pack :: [WindowsChar] -> WindowsString Source

Pack a list of platform words to a platform string.

Note that using this in conjunction with unsafeFromChar to convert from [Char] to platform string is probably not what you want, because it will truncate unicode code points.

String deconstruction

decodeUtf :: MonadThrow m => WindowsString -> m String Source

Partial unicode friendly decoding.

This decodes as UTF16-LE (strictly), which is a pretty good.

Throws a EncodingException if decoding fails.

decodeWith :: TextEncoding -> WindowsString -> Either EncodingException String Source

Decode a WindowsString with the specified encoding.

The String is forced into memory to catch all exceptions.

decodeFS :: WindowsString -> IO String Source

Like decodeUtf, except this mimics the behavior of the base library when doing filesystem operations (usually filepaths), which does permissive UTF-16 encoding, where coding errors generate Chars in the surrogate range.

The reason this is in IO is because it unifies with the Posix counterpart, which does require IO. unsafePerformIO/unsafeDupablePerformIO are safe, however.

decodeLE :: WindowsString -> IO String Source

Like decodeUtf, except this mimics the behavior of the base library when doing filesystem operations, which does permissive UTF-16 encoding, where coding errors generate Chars in the surrogate range.

The reason this is in IO is because it unifies with the Posix counterpart, which does require IO. unsafePerformIO/unsafeDupablePerformIO are safe, however.

unpack :: WindowsString -> [WindowsChar] Source

Unpack a platform string to a list of platform words.

Word construction

unsafeFromChar :: Char -> WindowsChar Source

Truncates to 2 octets.

Word deconstruction

toChar :: WindowsChar -> Char Source

Converts back to a unicode codepoint (total).

Basic interface

snoc :: WindowsString -> WindowsChar -> WindowsString Source

O(n) Append a byte to the end of a OsString

Since: os-string-1.4.200.0

cons :: WindowsChar -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

last :: HasCallStack => WindowsString -> WindowsChar Source

O(1) Extract the last element of a OsString, which must be finite and non-empty. An exception will be thrown in the case of an empty OsString.

This is a partial function, consider using unsnoc instead.

Since: os-string-1.4.200.0

tail :: HasCallStack => WindowsString -> WindowsString Source

O(n) Extract the elements after the head of a OsString, which must be non-empty. An exception will be thrown in the case of an empty OsString.

This is a partial function, consider using uncons instead.

Since: os-string-1.4.200.0

uncons :: WindowsString -> Maybe (WindowsChar, WindowsString) Source

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

Since: os-string-1.4.200.0

head :: HasCallStack => WindowsString -> WindowsChar Source

O(1) Extract the first element of a OsString, which must be non-empty. An exception will be thrown in the case of an empty OsString.

This is a partial function, consider using uncons instead.

Since: os-string-1.4.200.0

init :: HasCallStack => WindowsString -> WindowsString Source

O(n) Return all the elements of a OsString except the last one. An exception will be thrown in the case of an empty OsString.

This is a partial function, consider using unsnoc instead.

Since: os-string-1.4.200.0

unsnoc :: WindowsString -> Maybe (WindowsString, WindowsChar) Source

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

Since: os-string-1.4.200.0

null :: WindowsString -> Bool Source

O(1). The empty OsString.

Since: os-string-1.4.200.0

length :: WindowsString -> Int Source

O(1) The length of a OsString.

This returns the number of code units (Word8 on unix and Word16 on windows), not bytes.

>>> length "abc"
3

Since: os-string-1.4.200.0

Transforming OsString

map :: (WindowsChar -> WindowsChar) -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

reverse :: WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

intercalate :: WindowsString -> [WindowsString] -> WindowsString Source

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

Since: os-string-1.4.200.0

Reducing OsStrings (folds)

foldl :: (a -> WindowsChar -> a) -> a -> WindowsString -> a Source

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

Since: os-string-1.4.200.0

foldl' :: (a -> WindowsChar -> a) -> a -> WindowsString -> a Source

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

Since: os-string-1.4.200.0

foldl1 :: (WindowsChar -> WindowsChar -> WindowsChar) -> WindowsString -> WindowsChar Source

foldl1 is a variant of foldl that has no starting value argument, and thus must be applied to non-empty OsStrings. An exception will be thrown in the case of an empty OsString.

Since: os-string-1.4.200.0

foldl1' :: (WindowsChar -> WindowsChar -> WindowsChar) -> WindowsString -> WindowsChar Source

foldl1' is like foldl1, but strict in the accumulator. An exception will be thrown in the case of an empty OsString.

Since: os-string-1.4.200.0

foldr :: (WindowsChar -> a -> a) -> a -> WindowsString -> a Source

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

Since: os-string-1.4.200.0

foldr' :: (WindowsChar -> a -> a) -> a -> WindowsString -> a Source

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

Since: os-string-1.4.200.0

foldr1 :: (WindowsChar -> WindowsChar -> WindowsChar) -> WindowsString -> WindowsChar Source

foldr1 is a variant of foldr that has no starting value argument, and thus must be applied to non-empty OsStrings An exception will be thrown in the case of an empty OsString.

Since: os-string-1.4.200.0

foldr1' :: (WindowsChar -> WindowsChar -> WindowsChar) -> WindowsString -> WindowsChar Source

foldr1' is a variant of foldr1, but is strict in the accumulator.

Since: os-string-1.4.200.0

Special folds

all :: (WindowsChar -> Bool) -> WindowsString -> Bool Source

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

Since: os-string-1.4.200.0

any :: (WindowsChar -> Bool) -> WindowsString -> Bool Source

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

Since: os-string-1.4.200.0

concat :: [WindowsString] -> WindowsString Source

Generating and unfolding OsStrings

replicate :: Int -> WindowsChar -> WindowsString Source

O(n) replicate n x is a OsString of length n with x the value of every element. The following holds:

replicate w c = unfoldr w (\u -> Just (u,u)) c

Since: os-string-1.4.200.0

unfoldr :: (a -> Maybe (WindowsChar, a)) -> a -> WindowsString Source

O(n), where n is the length of the result. The unfoldr function is analogous to the List 'unfoldr'. unfoldr builds a OsString from a seed value. The function takes the element and returns Nothing if it is done producing the OsString or returns Just (a,b), in which case, a is the next byte in the string, and b is the seed value for further production.

This function is not efficient/safe. It will build a list of [Word8] and run the generator until it returns Nothing, otherwise recurse infinitely, then finally create a OsString.

If you know the maximum length, consider using unfoldrN.

Examples:

   unfoldr (\x -> if x <= 5 then Just (x, x + 1) else Nothing) 0
== pack [0, 1, 2, 3, 4, 5]

Since: os-string-1.4.200.0

unfoldrN :: Int -> (a -> Maybe (WindowsChar, a)) -> a -> (WindowsString, Maybe a) Source

O(n) Like unfoldr, unfoldrN builds a OsString from a seed value. However, the length of the result is limited by the first argument to unfoldrN. This function is more efficient than unfoldr when the maximum length of the result is known.

The following equation relates unfoldrN and unfoldr:

fst (unfoldrN n f s) == take n (unfoldr f s)

Since: os-string-1.4.200.0

Substrings

Breaking strings

take :: Int -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

takeEnd :: Int -> WindowsString -> WindowsString Source

O(n) 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: os-string-1.4.200.0

takeWhileEnd :: (WindowsChar -> Bool) -> WindowsString -> WindowsString Source

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

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

Since: os-string-1.4.200.0

takeWhile :: (WindowsChar -> Bool) -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

drop :: Int -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

dropEnd :: Int -> WindowsString -> WindowsString 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: os-string-1.4.200.0

dropWhileEnd :: (WindowsChar -> Bool) -> WindowsString -> WindowsString 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: os-string-1.4.200.0

dropWhile :: (WindowsChar -> Bool) -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

break :: (WindowsChar -> Bool) -> WindowsString -> (WindowsString, WindowsString) Source

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)).

Since: os-string-1.4.200.0

breakEnd :: (WindowsChar -> Bool) -> WindowsString -> (WindowsString, WindowsString) Source

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: os-string-1.4.200.0

span :: (WindowsChar -> Bool) -> WindowsString -> (WindowsString, WindowsString) Source

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).

Since: os-string-1.4.200.0

spanEnd :: (WindowsChar -> Bool) -> WindowsString -> (WindowsString, WindowsString) Source

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

Since: os-string-1.4.200.0

splitAt :: Int -> WindowsString -> (WindowsString, WindowsString) Source

O(n) splitAt n sbs is equivalent to (take n sbs, drop n sbs).

Since: os-string-1.4.200.0

split :: WindowsChar -> WindowsString -> [WindowsString] Source

O(n) Break a OsString 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 . (==)

Since: os-string-1.4.200.0

splitWith :: (WindowsChar -> Bool) -> WindowsString -> [WindowsString] Source

O(n) Splits a OsString 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 [""]

Since: os-string-1.4.200.0

stripSuffix :: WindowsString -> WindowsString -> Maybe WindowsString Source

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

Since: os-string-1.4.200.0

stripPrefix :: WindowsString -> WindowsString -> Maybe WindowsString Source

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

Since: os-string-1.4.200.0

Predicates

isInfixOf :: WindowsString -> WindowsString -> Bool Source

Check whether one string is a substring of another.

Since: os-string-1.4.200.0

isPrefixOf :: WindowsString -> WindowsString -> Bool Source

O(n) The isPrefixOf function takes two OsStrings and returns True

Since: os-string-1.4.200.0

isSuffixOf :: WindowsString -> WindowsString -> Bool Source

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

The following holds:

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

Since: os-string-1.4.200.0

Search for arbitrary susbstrings

breakSubstring :: WindowsString -> WindowsString -> (WindowsString, WindowsString) Source

Break a string on a substring, returning a pair of the part of the string prior to the match, and the rest of the string.

The following relationships hold:

break (== c) l == breakSubstring (singleton c) l

For example, to tokenise a string, dropping delimiters:

tokenise x y = h : if null t then [] else tokenise x (drop (length x) t)
    where (h,t) = breakSubstring x y

To skip to the first occurrence of a string:

snd (breakSubstring x y)

To take the parts of a string before a delimiter:

fst (breakSubstring x y)

Note that calling `breakSubstring x` does some preprocessing work, so you should avoid unnecessarily duplicating breakSubstring calls with the same pattern.

Since: os-string-1.4.200.0

Searching OsStrings

Searching by equality

elem :: WindowsChar -> WindowsString -> Bool Source

O(n) elem is the OsString membership predicate.

Since: os-string-1.4.200.0

find :: (WindowsChar -> Bool) -> WindowsString -> Maybe WindowsChar Source

O(n) The find function takes a predicate and a OsString, 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

Since: os-string-1.4.200.0

filter :: (WindowsChar -> Bool) -> WindowsString -> WindowsString Source

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

Since: os-string-1.4.200.0

partition :: (WindowsChar -> Bool) -> WindowsString -> (WindowsString, WindowsString) Source

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

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

Since: os-string-1.4.200.0

Indexing OsStrings

index :: HasCallStack => WindowsString -> Int -> WindowsChar Source

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

Since: os-string-1.4.200.0

indexMaybe :: WindowsString -> Int -> Maybe WindowsChar Source

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

0 <= n < length bs

Since: os-string-1.4.200.0

(!?) :: WindowsString -> Int -> Maybe WindowsChar Source

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

0 <= n < length bs

Since: os-string-1.4.200.0

elemIndex :: WindowsChar -> WindowsString -> Maybe Int Source

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

Since: os-string-1.4.200.0

elemIndices :: WindowsChar -> WindowsString -> [Int] Source

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

Since: os-string-1.4.200.0

count :: WindowsChar -> WindowsString -> Int Source

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

Since: os-string-1.4.200.0

findIndex :: (WindowsChar -> Bool) -> WindowsString -> Maybe Int Source

O(n) The findIndex function takes a predicate and a OsString and returns the index of the first element in the OsString satisfying the predicate.

Since: os-string-1.4.200.0

findIndices :: (WindowsChar -> Bool) -> WindowsString -> [Int] Source

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

Since: os-string-1.4.200.0