| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
RIO.Text
Description
Strict Text. Import as:
import qualified RIO.Text as T
This module does not export any partial functions. For those, see RIO.Text.Partial
Synopsis
- data Text
- pack :: String -> Text
- unpack :: Text -> String
- singleton :: Char -> Text
- empty :: Text
- cons :: Char -> Text -> Text
- snoc :: Text -> Char -> Text
- append :: Text -> Text -> Text
- uncons :: Text -> Maybe (Char, Text)
- null :: Text -> Bool
- length :: Text -> Int
- compareLength :: Text -> Int -> Ordering
- map :: (Char -> Char) -> Text -> Text
- intercalate :: Text -> [Text] -> Text
- intersperse :: Char -> Text -> Text
- transpose :: [Text] -> [Text]
- reverse :: Text -> Text
- toCaseFold :: Text -> Text
- toLower :: Text -> Text
- toUpper :: Text -> Text
- toTitle :: Text -> Text
- justifyLeft :: Int -> Char -> Text -> Text
- justifyRight :: Int -> Char -> Text -> Text
- center :: Int -> Char -> Text -> Text
- foldl :: (a -> Char -> a) -> a -> Text -> a
- foldl' :: (a -> Char -> a) -> a -> Text -> a
- foldr :: (Char -> a -> a) -> a -> Text -> a
- concat :: [Text] -> Text
- concatMap :: (Char -> Text) -> Text -> Text
- any :: (Char -> Bool) -> Text -> Bool
- all :: (Char -> Bool) -> Text -> Bool
- scanl :: (Char -> Char -> Char) -> Char -> Text -> Text
- scanl1 :: (Char -> Char -> Char) -> Text -> Text
- scanr :: (Char -> Char -> Char) -> Char -> Text -> Text
- scanr1 :: (Char -> Char -> Char) -> Text -> Text
- mapAccumL :: (a -> Char -> (a, Char)) -> a -> Text -> (a, Text)
- mapAccumR :: (a -> Char -> (a, Char)) -> a -> Text -> (a, Text)
- replicate :: Int -> Text -> Text
- unfoldr :: (a -> Maybe (Char, a)) -> a -> Text
- unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> Text
- take :: Int -> Text -> Text
- takeEnd :: Int -> Text -> Text
- drop :: Int -> Text -> Text
- dropEnd :: Int -> Text -> Text
- takeWhile :: (Char -> Bool) -> Text -> Text
- takeWhileEnd :: (Char -> Bool) -> Text -> Text
- dropWhile :: (Char -> Bool) -> Text -> Text
- dropWhileEnd :: (Char -> Bool) -> Text -> Text
- dropAround :: (Char -> Bool) -> Text -> Text
- strip :: Text -> Text
- stripStart :: Text -> Text
- stripEnd :: Text -> Text
- splitAt :: Int -> Text -> (Text, Text)
- break :: (Char -> Bool) -> Text -> (Text, Text)
- span :: (Char -> Bool) -> Text -> (Text, Text)
- group :: Text -> [Text]
- groupBy :: (Char -> Char -> Bool) -> Text -> [Text]
- inits :: Text -> [Text]
- tails :: Text -> [Text]
- split :: (Char -> Bool) -> Text -> [Text]
- chunksOf :: Int -> Text -> [Text]
- lines :: Text -> [Text]
- linesCR :: Text -> [Text]
- words :: Text -> [Text]
- unlines :: [Text] -> Text
- unwords :: [Text] -> Text
- isPrefixOf :: Text -> Text -> Bool
- isSuffixOf :: Text -> Text -> Bool
- isInfixOf :: Text -> Text -> Bool
- stripPrefix :: Text -> Text -> Maybe Text
- stripSuffix :: Text -> Text -> Maybe Text
- dropPrefix :: Text -> Text -> Text
- dropSuffix :: Text -> Text -> Text
- commonPrefixes :: Text -> Text -> Maybe (Text, Text, Text)
- filter :: (Char -> Bool) -> Text -> Text
- find :: (Char -> Bool) -> Text -> Maybe Char
- partition :: (Char -> Bool) -> Text -> (Text, Text)
- index :: HasCallStack => Text -> Int -> Char
- findIndex :: (Char -> Bool) -> Text -> Maybe Int
- zip :: Text -> Text -> [(Char, Char)]
- zipWith :: (Char -> Char -> Char) -> Text -> Text -> Text
- copy :: Text -> Text
- unpackCString# :: Addr# -> Text
- encodeUtf8 :: Text -> ByteString
- decodeUtf8With :: OnDecodeError -> ByteString -> Text
- decodeUtf8' :: ByteString -> Either UnicodeException Text
- lenientDecode :: OnDecodeError
Types
A space efficient, packed, unboxed Unicode text type.
Instances
Creation and elimination
O(1) Convert a character into a Text. Performs replacement on invalid scalar values.
Basic interface
cons :: Char -> Text -> Text infixr 5 #
O(n) Adds a character to the front of a Text. This function
is more costly than its List counterpart because it requires
copying a new array. Performs replacement on
invalid scalar values.
snoc :: Text -> Char -> Text #
O(n) Adds a character to the end of a Text. This copies the
entire array in the process.
Performs replacement on invalid scalar values.
compareLength :: Text -> Int -> Ordering #
O(min(n,c)) Compare the count of characters in a Text to a number.
compareLengtht c =compare(lengtht) c
This function gives the same answer as comparing against the result
of length, but can short circuit if the count of characters is
greater than the number, and hence be more efficient.
Transformations
intercalate :: Text -> [Text] -> Text #
O(n) The intercalate function takes a Text and a list of
Texts and concatenates the list after interspersing the first
argument between each element of the list.
Example:
>>>T.intercalate "NI!" ["We", "seek", "the", "Holy", "Grail"]"WeNI!seekNI!theNI!HolyNI!Grail"
intersperse :: Char -> Text -> Text #
O(n) The intersperse function takes a character and places it
between the characters of a Text.
Example:
>>>T.intersperse '.' "SHIELD""S.H.I.E.L.D"
Performs replacement on invalid scalar values.
transpose :: [Text] -> [Text] #
O(n) The transpose function transposes the rows and columns
of its Text argument. Note that this function uses pack,
unpack, and the list version of transpose, and is thus not very
efficient.
Examples:
>>>transpose ["green","orange"]["go","rr","ea","en","ng","e"]
>>>transpose ["blue","red"]["br","le","ud","e"]
Case conversion
toCaseFold :: Text -> Text #
O(n) Convert a string to folded case.
This function is mainly useful for performing caseless (also known as case insensitive) string comparisons.
A string x is a caseless match for a string y if and only if:
toCaseFold x == toCaseFold y
The result string may be longer than the input string, and may
differ from applying toLower to the input string. For instance,
the Armenian small ligature "ﬓ" (men now, U+FB13) is case
folded to the sequence "մ" (men, U+0574) followed by
"ն" (now, U+0576), while the Greek "µ" (micro sign,
U+00B5) is case folded to "μ" (small letter mu, U+03BC)
instead of itself.
O(n) Convert a string to lower case, using simple case conversion.
The result string may be longer than the input string. For instance, "İ" (Latin capital letter I with dot above, U+0130) maps to the sequence "i" (Latin small letter i, U+0069) followed by " ̇" (combining dot above, U+0307).
O(n) Convert a string to upper case, using simple case conversion.
The result string may be longer than the input string. For instance, the German "ß" (eszett, U+00DF) maps to the two-letter sequence "SS".
O(n) Convert a string to title case, using simple case conversion.
The first letter (as determined by isLetter)
of the input is converted to title case, as is
every subsequent letter that immediately follows a non-letter.
Every letter that immediately follows another letter is converted
to lower case.
This function is not idempotent.
Consider lower-case letter ʼn (U+0149 LATIN SMALL LETTER N PRECEDED BY APOSTROPHE).
Then toTitle "ʼn" = "ʼN": the first (and the only) letter of the input
is converted to title case, becoming two letters.
Now ʼ (U+02BC MODIFIER LETTER APOSTROPHE) is a modifier letter
and as such is recognised as a letter by isLetter,
so toTitle "ʼN" = "'n".
The result string may be longer than the input string. For example, the Latin small ligature fl (U+FB02) is converted to the sequence Latin capital letter F (U+0046) followed by Latin small letter l (U+006C).
Note: this function does not take language or culture specific rules into account. For instance, in English, different style guides disagree on whether the book name "The Hill of the Red Fox" is correctly title cased—but this function will capitalize every word.
Since: text-1.0.0.0
Justification
justifyLeft :: Int -> Char -> Text -> Text #
O(n) Left-justify a string to the given length, using the specified fill character on the right. Performs replacement on invalid scalar values.
Examples:
>>>justifyLeft 7 'x' "foo""fooxxxx"
>>>justifyLeft 3 'x' "foobar""foobar"
justifyRight :: Int -> Char -> Text -> Text #
O(n) Right-justify a string to the given length, using the specified fill character on the left. Performs replacement on invalid scalar values.
Examples:
>>>justifyRight 7 'x' "bar""xxxxbar"
>>>justifyRight 3 'x' "foobar""foobar"
center :: Int -> Char -> Text -> Text #
O(n) Center a string to the given length, using the specified fill character on either side. Performs replacement on invalid scalar values.
Examples:
>>>center 8 'x' "HS""xxxHSxxx"
Folds
foldr :: (Char -> a -> a) -> a -> Text -> a #
O(n) foldr, applied to a binary operator, a starting value
(typically the right-identity of the operator), and a Text,
reduces the Text using the binary operator, from right to left.
If the binary operator is strict in its second argument, use foldr'
instead.
foldr is lazy like foldr for lists: evaluation actually
traverses the Text from left to right, only as far as it needs to.
For example, head can be defined with O(1) complexity using foldr:
head :: Text -> Char head = foldr const (error "head empty")
Searches from left to right with short-circuiting behavior can
also be defined using foldr (e.g., any, all, find, elem).
Special folds
Construction
Scans
Accumulating maps
mapAccumR :: (a -> Char -> (a, Char)) -> a -> Text -> (a, Text) #
The mapAccumR function behaves like a combination of map and
a strict foldr; it applies a function to each element of a
Text, passing an accumulating parameter from right to left, and
returning a final value of this accumulator together with the new
Text.
Performs replacement on invalid scalar values.
Generation and unfolding
unfoldr :: (a -> Maybe (Char, a)) -> a -> Text #
O(n), where n is the length of the result. The unfoldr
function is analogous to the List unfoldr. unfoldr builds a
Text from a seed value. The function takes the element and
returns Nothing if it is done producing the Text, otherwise
Just (a,b). In this case, a is the next Char in the
string, and b is the seed value for further production.
Performs replacement on invalid scalar values.
unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> Text #
O(n) Like unfoldr, unfoldrN builds a Text from a seed
value. However, the length of the result should be limited by the
first argument to unfoldrN. This function is more efficient than
unfoldr when the maximum length of the result is known and
correct, otherwise its performance is similar to unfoldr.
Performs replacement on invalid scalar values.
Substrings
Breaking strings
takeEnd :: Int -> Text -> Text #
O(n) takeEnd n t returns the suffix remaining after
taking n characters from the end of t.
Examples:
>>>takeEnd 3 "foobar""bar"
Since: text-1.1.1.0
dropEnd :: Int -> Text -> Text #
O(n) dropEnd n t returns the prefix remaining after
dropping n characters from the end of t.
Examples:
>>>dropEnd 3 "foobar""foo"
Since: text-1.1.1.0
takeWhileEnd :: (Char -> Bool) -> Text -> Text #
O(n) takeWhileEnd, applied to a predicate p and a Text,
returns the longest suffix (possibly empty) of elements that
satisfy p.
Examples:
>>>takeWhileEnd (=='o') "foo""oo"
Since: text-1.2.2.0
dropWhileEnd :: (Char -> Bool) -> Text -> Text #
O(n) dropWhileEnd p t returns the prefix remaining after
dropping characters that satisfy the predicate p from the end of
t.
Examples:
>>>dropWhileEnd (=='.') "foo...""foo"
dropAround :: (Char -> Bool) -> Text -> Text #
O(n) dropAround p t returns the substring remaining after
dropping characters that satisfy the predicate p from both the
beginning and end of t.
O(n) Remove leading and trailing white space from a string. Equivalent to:
dropAround isSpace
stripStart :: Text -> Text #
O(n) Remove leading white space from a string. Equivalent to:
dropWhile isSpace
O(n) Remove trailing white space from a string. Equivalent to:
dropWhileEnd isSpace
span :: (Char -> Bool) -> Text -> (Text, Text) #
O(n) span, applied to a predicate p and text t, returns
a pair whose first element is the longest prefix (possibly empty)
of t of elements that satisfy p, and whose second is the
remainder of the text.
>>>T.span (=='0') "000AB"("000","AB")
groupBy :: (Char -> Char -> Bool) -> Text -> [Text] #
O(n) Group characters in a string according to a predicate.
Breaking into many substrings
split :: (Char -> Bool) -> Text -> [Text] #
O(n) Splits a Text 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.
>>>split (=='a') "aabbaca"["","","bb","c",""]
>>>split (=='a') ""[""]
chunksOf :: Int -> Text -> [Text] #
O(n) Splits a Text into components of length k. The last
element may be shorter than the other chunks, depending on the
length of the input. Examples:
>>>chunksOf 3 "foobarbaz"["foo","bar","baz"]
>>>chunksOf 4 "haskell.org"["hask","ell.","org"]
Breaking into lines and words
Predicates
isPrefixOf :: Text -> Text -> Bool #
O(n) The isPrefixOf function takes two Texts and returns
True if and only if the first is a prefix of the second.
isSuffixOf :: Text -> Text -> Bool #
O(n) The isSuffixOf function takes two Texts and returns
True if and only if the first is a suffix of the second.
View patterns
stripPrefix :: Text -> Text -> Maybe Text #
O(n) Return the suffix of the second string if its prefix matches the entire first string.
Examples:
>>>stripPrefix "foo" "foobar"Just "bar"
>>>stripPrefix "" "baz"Just "baz"
>>>stripPrefix "foo" "quux"Nothing
This is particularly useful with the ViewPatterns extension to
GHC, as follows:
{-# LANGUAGE ViewPatterns #-}
import Data.Text as T
fnordLength :: Text -> Int
fnordLength (stripPrefix "fnord" -> Just suf) = T.length suf
fnordLength _ = -1stripSuffix :: Text -> Text -> Maybe Text #
O(n) Return the prefix of the second string if its suffix matches the entire first string.
Examples:
>>>stripSuffix "bar" "foobar"Just "foo"
>>>stripSuffix "" "baz"Just "baz"
>>>stripSuffix "foo" "quux"Nothing
This is particularly useful with the ViewPatterns extension to
GHC, as follows:
{-# LANGUAGE ViewPatterns #-}
import Data.Text as T
quuxLength :: Text -> Int
quuxLength (stripSuffix "quux" -> Just pre) = T.length pre
quuxLength _ = -1Drop prefix if present, otherwise return original Text.
Since: 0.0.0.0
Drop prefix if present, otherwise return original Text.
Since: 0.0.0.0
commonPrefixes :: Text -> Text -> Maybe (Text, Text, Text) #
O(n) Find the longest non-empty common prefix of two strings and return it, along with the suffixes of each string at which they no longer match.
If the strings do not have a common prefix or either one is empty,
this function returns Nothing.
Examples:
>>>commonPrefixes "foobar" "fooquux"Just ("foo","bar","quux")
>>>commonPrefixes "veeble" "fetzer"Nothing
>>>commonPrefixes "" "baz"Nothing
Searching
Indexing
index :: HasCallStack => Text -> Int -> Char #
O(n) Text index (subscript) operator, starting from 0.
Zipping
Low level operations
O(n) Make a distinct copy of the given string, sharing no storage with the original string.
As an example, suppose you read a large string, of which you need
only a small portion. If you do not use copy, the entire original
array will be kept alive in memory by the smaller string. Making a
copy "breaks the link" to the original array, allowing it to be
garbage collected if there are no other live references to it.
unpackCString# :: Addr# -> Text #
O(n) Convert a null-terminated
modified UTF-8
(but with a standard UTF-8 representation of characters from supplementary planes)
string to a Text. Counterpart to unpackCStringUtf8#.
No validation is performed, malformed input can lead to memory access violation.
Since: text-1.2.1.1
Encoding
encodeUtf8 :: Text -> ByteString #
Encode text using UTF-8 encoding.
decodeUtf8With :: OnDecodeError -> ByteString -> Text #
Decode a ByteString containing UTF-8 encoded text.
Surrogate code points in replacement character returned by OnDecodeError
will be automatically remapped to the replacement char U+FFFD.
decodeUtf8' :: ByteString -> Either UnicodeException Text #
Decode a ByteString containing UTF-8 encoded text.
If the input contains any invalid UTF-8 data, the relevant exception will be returned, otherwise the decoded text.
lenientDecode :: OnDecodeError #
Replace an invalid input byte with the Unicode replacement character U+FFFD.