Text.Megaparsec.Char

Commonly used character parsers.

Simple parsers

newline :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a newline character.

crlf :: (MonadParsec e s m, Token s ~ Char) => m String

Parses a carriage return character followed by a newline character. Returns sequence of characters parsed.

eol :: (MonadParsec e s m, Token s ~ Char) => m String

Parses a CRLF (see crlf) or LF (see newline) end of line. Returns the sequence of characters parsed.

eol = (pure <$> newline) <|> crlf

tab :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a tab character.

space :: (MonadParsec e s m, Token s ~ Char) => m ()

Skips zero or more white space characters.

See also: skipMany and spaceChar.

Categories of characters

controlChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses control characters, which are the non-printing characters of the Latin-1 subset of Unicode.

spaceChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a Unicode space character, and the control characters: tab, newline, carriage return, form feed, and vertical tab.

upperChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses an upper-case or title-case alphabetic Unicode character. Title case is used by a small number of letter ligatures like the single-character form of Lj.

lowerChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a lower-case alphabetic Unicode character.

letterChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses alphabetic Unicode characters: lower-case, upper-case and title-case letters, plus letters of case-less scripts and modifiers letters.

alphaNumChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses alphabetic or numeric digit Unicode characters.

Note that numeric digits outside the ASCII range are parsed by this parser but not by digitChar. Such digits may be part of identifiers but are not used by the printer and reader to represent numbers.

printChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses printable Unicode characters: letters, numbers, marks, punctuation, symbols and spaces.

digitChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses an ASCII digit, i.e between “0” and “9”.

octDigitChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses an octal digit, i.e. between “0” and “7”.

hexDigitChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a hexadecimal digit, i.e. between “0” and “9”, or “a” and “f”, or “A” and “F”.

markChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses Unicode mark characters, for example accents and the like, which combine with preceding characters.

numberChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses Unicode numeric characters, including digits from various scripts, Roman numerals, et cetera.

punctuationChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses Unicode punctuation characters, including various kinds of connectors, brackets and quotes.

symbolChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses Unicode symbol characters, including mathematical and currency symbols.

separatorChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses Unicode space and separator characters.

asciiChar :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a character from the first 128 characters of the Unicode character set, corresponding to the ASCII character set.

latin1Char :: (MonadParsec e s m, Token s ~ Char) => m Char

Parses a character from the first 256 characters of the Unicode character set, corresponding to the ISO 8859-1 (Latin-1) character set.

charCategory :: (MonadParsec e s m, Token s ~ Char) => GeneralCategory -> m Char

charCategory cat Parses character in Unicode General Category cat, see GeneralCategory.

categoryName :: GeneralCategory -> String

Returns human-readable name of Unicode General Category.

More general parsers

char :: (MonadParsec e s m, Token s ~ Char) => Char -> m Char

char c parses a single character c.

semicolon = char ';'

char' :: (MonadParsec e s m, Token s ~ Char) => Char -> m Char

The same as char but case-insensitive. This parser returns actually parsed character preserving its case.

>>> parseTest (char' 'e') "E"
'E'
>>> parseTest (char' 'e') "G"
1:1:
unexpected 'G'
expecting 'E' or 'e'

anyChar :: (MonadParsec e s m, Token s ~ Char) => m Char

This parser succeeds for any character. Returns the parsed character.

oneOf :: (Foldable f, MonadParsec e s m, Token s ~ Char) => f Char -> m Char

oneOf cs succeeds if the current character is in the supplied list of characters cs. Returns the parsed character. Note that this parser doesn't automatically generate “expected” component of error message, so usually you should label it manually with label or (<?>).

See also: satisfy.

digit = oneOf ['0'..'9'] <?> "digit"

oneOf' :: (Foldable f, MonadParsec e s m, Token s ~ Char) => f Char -> m Char

The same as oneOf, but case-insensitive. Returns the parsed character preserving its case.

vowel = oneOf' "aeiou" <?> "vowel"

noneOf :: (Foldable f, MonadParsec e s m, Token s ~ Char) => f Char -> m Char

As the dual of oneOf, noneOf cs succeeds if the current character not in the supplied list of characters cs. Returns the parsed character.

noneOf' :: (Foldable f, MonadParsec e s m, Token s ~ Char) => f Char -> m Char

The same as noneOf, but case-insensitive.

consonant = noneOf' "aeiou" <?> "consonant"

satisfy :: (MonadParsec e s m, Token s ~ Char) => (Char -> Bool) -> m Char

The parser satisfy f succeeds for any character for which the supplied function f returns True. Returns the character that is actually parsed.

digitChar = satisfy isDigit <?> "digit"
oneOf cs  = satisfy (`elem` cs)

Sequence of characters

string :: (MonadParsec e s m, Token s ~ Char) => String -> m String

string s parses a sequence of characters given by s. Returns the parsed string (i.e. s).

divOrMod = string "div" <|> string "mod"

string' :: (MonadParsec e s m, Token s ~ Char) => String -> m String

The same as string, but case-insensitive. On success returns string cased as actually parsed input.

>>> parseTest (string' "foobar") "foObAr"
"foObAr"