Data.String.CodeUnits - purescript-strings - Pursuit (original) (raw)

Package

purescript-strings

Repository

purescript/purescript-strings

#stripPrefix Source

stripPrefix :: Pattern -> String -> Maybe String

If the string starts with the given prefix, return the portion of the string left after removing it, as a Just value. Otherwise, return Nothing.

stripPrefix (Pattern "http:") "http://purescript.org" == Just "//purescript.org"
stripPrefix (Pattern "http:") "https://purescript.org" == Nothing

#stripSuffix Source

stripSuffix :: Pattern -> String -> Maybe String

If the string ends with the given suffix, return the portion of the string left after removing it, as a Just value. Otherwise, returnNothing.

stripSuffix (Pattern ".exe") "psc.exe" == Just "psc"
stripSuffix (Pattern ".exe") "psc" == Nothing

#contains Source

contains :: Pattern -> String -> Boolean

Checks whether the pattern appears in the given string.

contains (Pattern "needle") "haystack with needle" == true
contains (Pattern "needle") "haystack" == false

#charAt Source

charAt :: Int -> String -> Maybe Char

Returns the character at the given index, if the index is within bounds.

charAt 2 "Hello" == Just 'l'
charAt 10 "Hello" == Nothing

#toChar Source

toChar :: String -> Maybe Char

Converts the string to a character, if the length of the string is exactly 1.

toChar "l" == Just 'l'
toChar "Hi" == Nothing -- since length is not 1

#uncons Source

uncons :: String -> Maybe { head :: Char, tail :: String }

Returns the first character and the rest of the string, if the string is not empty.

uncons "" == Nothing
uncons "Hello World" == Just { head: 'H', tail: "ello World" }

#length Source

length :: String -> Int

Returns the number of characters the string is composed of.

length "Hello World" == 11

#countPrefix Source

countPrefix :: (Char -> Boolean) -> String -> Int

Returns the number of contiguous characters at the beginning of the string for which the predicate holds.

countPrefix (_ /= ' ') "Hello World" == 5 -- since length "Hello" == 5

#indexOf Source

indexOf :: Pattern -> String -> Maybe Int

Returns the index of the first occurrence of the pattern in the given string. Returns Nothing if there is no match.

indexOf (Pattern "c") "abcdc" == Just 2
indexOf (Pattern "c") "aaa" == Nothing

#indexOf' Source

indexOf' :: Pattern -> Int -> String -> Maybe Int

Returns the index of the first occurrence of the pattern in the given string, starting at the specified index. Returns Nothing if there is no match.

indexOf' (Pattern "a") 2 "ababa" == Just 2
indexOf' (Pattern "a") 3 "ababa" == Just 4

#lastIndexOf Source

lastIndexOf :: Pattern -> String -> Maybe Int

Returns the index of the last occurrence of the pattern in the given string. Returns Nothing if there is no match.

lastIndexOf (Pattern "c") "abcdc" == Just 4
lastIndexOf (Pattern "c") "aaa" == Nothing

#lastIndexOf' Source

lastIndexOf' :: Pattern -> Int -> String -> Maybe Int

Returns the index of the last occurrence of the pattern in the given string, starting at the specified index and searching backwards towards the beginning of the string.

Starting at a negative index is equivalent to starting at 0 and starting at an index greater than the string length is equivalent to searching in the whole string.

Returns Nothing if there is no match.

lastIndexOf' (Pattern "a") (-1) "ababa" == Just 0
lastIndexOf' (Pattern "a") 1 "ababa" == Just 0
lastIndexOf' (Pattern "a") 3 "ababa" == Just 2
lastIndexOf' (Pattern "a") 4 "ababa" == Just 4
lastIndexOf' (Pattern "a") 5 "ababa" == Just 4

#takeWhile Source

takeWhile :: (Char -> Boolean) -> String -> String

Returns the longest prefix (possibly empty) of characters that satisfy the predicate.

takeWhile (_ /= ':') "http://purescript.org" == "http"

#slice Source

slice :: Int -> Int -> String -> String

Returns the substring at indices [begin, end). If either index is negative, it is normalised to length s - index, where s is the input string. "" is returned if either index is out of bounds or if begin > end after normalisation.

slice 0 0   "purescript" == ""
slice 0 1   "purescript" == "p"
slice 3 6   "purescript" == "esc"
slice (-4) (-1) "purescript" == "rip"
slice (-4) 3  "purescript" == ""

#splitAt Source

splitAt :: Int -> String -> { after :: String, before :: String }

Splits a string into two substrings, where before contains the characters up to (but not including) the given index, and after contains the rest of the string, from that index on.

splitAt 2 "Hello World" == { before: "He", after: "llo World"}
splitAt 10 "Hi" == { before: "Hi", after: ""}

Thus the length of (splitAt i s).before will equal either i orlength s, if that is shorter. (Or if i is negative the length will be 0.)

In code:

length (splitAt i s).before == min (max i 0) (length s)
(splitAt i s).before <> (splitAt i s).after == s
splitAt i s == {before: take i s, after: drop i s}