character

parsley.character$

This module contains many parsers to do with reading one or more characters. Almost every parser will need something from this module.

In particular, this module contains: combinators that can read specific characters; combinators that represent character classes and their negations; combinators for reading specific strings; as well as a selection of pre-made parsers to parse specific kinds of character, like digits and letters.

Attributes

Since:: 2.2.0
Source:: character.scala
Graph
Supertypes: class Object
trait Matchable
class Any
Self type: character.type

Members list

Concise view

Core Combinators and Parsers

These are the most primitive combinators for consuming input capable of any input reading tasks.

This combinator tries to parse a single specific character c from the input.

Attempts to read the given character c from the input stream at the current position. If this character can be found, it is consumed and returned. Otherwise, no input is consumed and this combinator will fail.

Attributes

c

the character to parse

Returns:

a parser that tries to read a single c, or fails.

Note:

this combinator can only handle 16-bit characters: for larger codepoints, consider using string.

Example:

scala> import parsley.character.char
scala> char('a').parse("")
val res0 = Failure(..)
scala> char('a').parse("a")
val res1 = Success('a')
scala> char('a').parse("ba")
val res2 = Failure(..)

Source:

character.scala

This parser will parse any single character from the input, failing if there is no input remaining.

Attributes

Note:: this combinator can only handle 16-bit characters.
Source:: character.scala

This combinator tries to parse a single character from the input that matches the given predicate.

Attempts to read a character from the input and tests it against the predicate pred. If a character c can be read and pred(c) is true, then c is consumed and returned. Otherwise, no input is consumed and this combinator will fail.

Attributes

pred

the predicate to test the next character against, should one exist.

Returns:

a parser that tries to read a single character c, such that pred(c) is true, or fails.

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.satisfy
scala> satisfy(_.isDigit).parse("")
val res0 = Failure(..)
scala> satisfy(_.isDigit).parse("7")
val res1 = Success('7')
scala> satisfy(_.isDigit).parse("a5")
val res2 = Failure(..)
scala> def char(c: Char): Parsley[Char] = satisfy(_ == c)

Source:

character.scala

Character Class Combinators

These combinators allow for working with character classes. This means that a set, or range, of characters can be specified, and the combinator will return a parser that matches one of those characters (or conversely, any character that is not in that set). The parsed character is always returned.

This combinator tries to parse any character not from supplied set of characters cs, returning it if successful.

If the next character in the input is not a member of the set cs, it is consumed and returned. Otherwise, no input is consumed and the combinator fails.

Attributes

cs

the set of characters to check.

Returns:

a parser that parses one character that is not a member of the set cs.

See also:

satisfy

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.noneOf
scala> val p = noneOf(Set('a', 'b', 'c'))
scala> p.parse("a")
val res0 = Failure(..)
scala> p.parse("c")
val res1 = Failure(..)
scala> p.parse("xb")
val res2 = Success('x')
scala> p.parse("")
val res3 = Failure(..)

Source:

character.scala

This combinator tries to parse any character not from supplied set of characters cs, returning it if successful.

If the next character in the input is not an element of the list of characters cs, it is consumed and returned. Otherwise, no input is consumed and the combinator fails.

Attributes

cs

the set of characters to check.

Returns:

a parser that parses one character that is not an element of cs.

See also:

satisfy

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.noneOf
scala> val p = noneOf('a', 'b', 'c')
scala> p.parse("a")
val res0 = Failure(..)
scala> p.parse("c")
val res1 = Failure(..)
scala> p.parse("xb")
val res2 = Success('x')
scala> p.parse("")
val res3 = Failure(..)

Source:

character.scala

This combinator tries to parse any character not from supplied set of characters cs, returning it if successful.

If the next character in the input is outside of the range of characters cs, it is consumed and returned. Otherwise, no input is consumed and the combinator fails.

Attributes

cs

the range of characters to check.

Returns:

a parser that parses a character outside the range cs.

See also:

satisfy

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.noneOf
scala> val p = noneOf('a' to 'c')
scala> p.parse("a")
val res0 = Failure(..)
scala> p.parse("b")
val res1 = Failure(..)
scala> p.parse("c")
val res1 = Failure(..)
scala> p.parse("xb")
val res2 = Success('x')
scala> p.parse("")
val res3 = Failure(..)

Source:

character.scala

This combinator tries to parse any character from supplied set of characters cs, returning it if successful.

If the next character in the input is a member of the set cs, it is consumed and returned. Otherwise, no input is consumed and the combinator fails.

Attributes

cs

the set of characters to check.

Returns:

a parser that parses one of the member of the set cs.

See also:

satisfy

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.oneOf
scala> val p = oneOf(Set('a', 'b', 'c'))
scala> p.parse("a")
val res0 = Success('a')
scala> p.parse("c")
val res1 = Success('c')
scala> p.parse("xb")
val res2 = Failure(..)

Source:

character.scala

This combinator tries to parse any character from supplied set of characters cs, returning it if successful.

If the next character in the input is an element of the list of characters cs, it is consumed and returned. Otherwise, no input is consumed and the combinator fails.

Attributes

cs

the characters to check.

Returns:

a parser that parses one of the elements of cs.

See also:

satisfy

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.oneOf
scala> val p = oneOf('a', 'b', 'c')
scala> p.parse("a")
val res0 = Success('a')
scala> p.parse("c")
val res1 = Success('c')
scala> p.parse("xb")
val res2 = Failure(..)

Source:

character.scala

This combinator tries to parse any character from supplied set of characters cs, returning it if successful.

If the next character in the input is within the range of characters cs, it is consumed and returned. Otherwise, no input is consumed and the combinator fails.

Attributes

cs

the range of characters to check.

Returns:

a parser that parses a character within the range cs.

See also:

satisfy

Note:

this combinator can only handle 16-bit characters.

Example:

scala> import parsley.character.oneOf
scala> val p = oneOf('a' to 'c')
scala> p.parse("a")
val res0 = Success('a')
scala> p.parse("b")
val res1 = Success('b')
scala> p.parse("c")
val res1 = Success('c')
scala> p.parse("xb")
val res2 = Failure(..)

Source:

character.scala

String Combinators

These combinators allow for working with, or building, strings. This means that they can parse specific strings, specific sets of strings, or can read characters repeatedly to generate strings. They are united in all returning String as their result.

This combinator attempts to parse a given string from the input, and fails otherwise.

Attempts to read the given string completely from the input at the current position. If the string is present, then the parser succeeds, and the entire string is consumed from the input. Otherwise, if the input has too few characters remaining, or not all the characters matched, the parser fails. On failure, all the characters that were matched are consumed from the input.

Attributes

s

the string to be parsed from the input

Returns:

a parser that either parses the string s or fails at the first mismatched character.

Note:

the error messages generated by string do not reflect how far into the input it managed to get: this is because the error being positioned at the start of the string is more natural. However, input will still be consumed for purposes of backtracking.

Example:

scala> import parsley.character.string
scala> string("abc").parse("")
val res0 = Failure(..)
scala> string("abc").parse("abcd")
val res1 = Success("abc")
scala> string("abc").parse("xabc")
val res2 = Failure(..)

Source:

character.scala

This combinator parses pc zero or more times, collecting its results into a string.

Parses pc repeatedly until it fails. The resulting characters are placed into a string, which is then returned. This is morally equivalent to many(pc).map(_.mkString), but it uses StringBuilder, which makes it much more efficient.

Attributes

pc

the parser whose results make up the string

Returns:

a parser that parses a string whose letters consist of results from pc.

Since:

4.0.0

Example:

scala> import parsley.character.{letter, letterOrDigit, stringOfMany}
scala> import parsley.implicits.zipped.Zipped2
scala> val ident = (letter, stringOfMany(letterOrDigit)).zipped((c, s) => s"&#36;c&#36;s")
scala> ident.parse("abdc9d")
val res0 = Success("abdc9d")
scala> ident.parse("a")
val res1 = Success("a")
scala> ident.parse("9")
val res2 = Failure(..)

Source:

character.scala

This combinator parses pc one or more times, collecting its results into a string.

Attributes

pc

the parser whose results make up the string

Returns:

a parser that parses a string whose letters consist of results from pc.

Since:

4.0.0

Example:

scala> import parsley.character.{letter, stringOfSome}
scala> val ident = stringOfSome(letter)
scala> ident.parse("abdc9d")
val res0 = Success("abdc")
scala> ident.parse("")
val res1 = Failure(..)

Source:

character.scala

This combinator tries to parse each of the strings strs (and str0), until one of them succeeds.

Unlike choice, or more accurately attemptChoice, this combinator will not necessarily parse the strings in the order provided. It will favour strings that have another string as a prefix first, so that it has Longest Match semantics. It will try to minimise backtracking too, making it a much more efficient option than attemptChoice.

The longest succeeding string will be returned. If no strings match then the combinator fails.

Attributes

str0

the first string to try to parse.

strs

the remaining strings to try to parse.

Returns:

a parser that tries to parse all the given strings returning the longest one that matches.

Since:

4.0.0

Example:

scala> import parsley.character.strings
scala> val p = strings("hell", "hello", "goodbye", "g", "abc")
scala> p.parse("hell")
val res0 = Success("hell")
scala> p.parse("hello")
val res1 = Success("hello")
scala> p.parse("good")
val res2 = Success("g")
scala> p.parse("goodbye")
val res3 = Success("goodbye")
scala> p.parse("a")
val res4 = Failure(..)

Source:

character.scala

This combinator tries to parse each of the key-value pairs kvs (and kv0), until one of them succeeds.

Each argument to this combinator is a pair of a string and a parser to perform if that string can be parsed. strings(s0 -> p0, ...) can be thought of as attemptChoice(string(s0) *> p0, ...), however, the given ordering of key-value pairs does not dictate the order in which the parses are tried. In particular, it will favour keys that are the prefix of another key first, so that it has Longest Match semantics. it will try to minimise backtracking too, making it a much more efficient option than attemptChoice.

Attributes

kv0

the first key-value pair to try to parse.

kvs

the remaining key-value pairs to try to parse.

Returns:

a parser that tries to parse all the given key-value pairs, returning the (possibly failing) result of the value that corresponds to the longest matching key.

Since:

4.0.0

Note:

the scope of any backtracking performed is isolated to the key itself, as it is assumed that once a key parses correctly, the branch has been committed to. Putting an attempt around the values will not affect this behaviour.

Example:

scala> import parsley.character.strings
scala> val p = strings("hell" -> pure(4), "hello" -> pure(5), "goodbye" -> pure(7), "g" -> pure(1), "abc" -> pure(3))
scala> p.parse("hell")
val res0 = Success(4)
scala> p.parse("hello")
val res1 = Success(5)
scala> p.parse("good")
val res2 = Success(1)
scala> p.parse("goodbye")
val res3 = Success(7)
scala> p.parse("a")
val res4 = Failure(..)

Source:

character.scala

Specific Character Parsers

These parsers are special cases of satisfy or char. They are worth using, as they are given special error labelling, producing nicer error messages than their primitive counterparts. This documentation assumes JDK 17. JDK 17 is compliant with Unicode® Specification 13.0. As such, the descriptions of the parsers in this section are accurate with respect to Unicode® Specification 13.0: using a different JDK may affect the precise definitions of the parsers below. If in doubt, check the documentation for java.lang.Character to see which Unicode version is supported by your JVM. A table of the Unicode versions up to JDK 17 can be found here. These parsers are only able to parse unicode characters in the range '\u0000' to '\uFFFF', known as the Basic Multilingual Plane (BMP). Unicode characters wider than a single 16-bit character should be parsed using multi-character combinators such as string, or, alternatively, satisfyUtf16 or charUtf16.

This parser tries to parse a bit and returns it if successful.

A bit (binary digit) is either '0' or '1'.

Attributes

Source:: character.scala

This parser tries to parse a CRLF newline character pair, returning '\n' if successful.

A CRLF character is the pair of carriage return ('\r') and line feed ('\n'). These two characters will be parsed together or not at all. The parser is made atomic using attempt.

Attributes

Source:: character.scala

This parser tries to parse a digit, and returns it if successful.

A digit is any character c <= '\uFFFF' whose Unicode Category Type is Decimal Number (Nd). Examples of (inclusive) ranges within this category include:

the Latin digits '0' through '9'
the Arabic-Indic digits '\u0660' through '\u0669'
the Extended Arabic-Indic digits '\u06F0' through '\u06F9'
the Devangari digits '\u0966' through '\u096F'
the Fullwidth digits '\uFF10' through '\uFF19'

The full list of codepoints found in a category can be found in the Unicode Character Database.

Attributes

Source:: character.scala

This parser will parse either a line feed (LF) or a CRLF newline, returning '\n' if successful.

Attributes

See also:: crlf
Source:: character.scala

This parser tries to parse a hexadecimal digit, and returns it if successful.

A hexadecimal digit is one of (all inclusive ranges):

the digits '0' through '9'
the letters 'a' through 'f'
the letters 'A' through 'Z'

Attributes

See also:: isHexDigit
Source:: character.scala

This parser tries to parse a letter, and returns it if successful.

A letter is any character c <= '\uFFFF' whose Unicode Category Type is any of the following:

Uppercase Letter (Lu)
Lowercase Letter (Ll)
Titlecase Letter (Lt)
Modifier Letter (Lm)
Other Letter (Lo)

The full list of codepoints found in a category can be found in the Unicode Character Database.

Attributes

Source:: character.scala

This parser tries to parse either a letter or a digit, and returns it if successful.

A letter or digit is anything that would parse in either letter or digit.

Attributes

See also:: documentation for letter.
documentation for digit.
Source:: character.scala

This parser tries to parse a lowercase letter, and returns it if successful.

A lowercase letter is any character c <= '\uFFFF' whose Unicode Category Type is Lowercase Letter (Ll). Examples of characters within this category include:

the Latin letters 'a' through 'z'
Latin special character such as 'é', 'ß', 'ð'
Cryillic letters
Greek letters
Coptic letters

The full list of codepoints found in a category can be found in the Unicode Character Database.

Attributes

Source:: character.scala

This parser tries to parse a line feed newline ('\n') character, and returns it if successful.

This parser will not accept a carriage return (CR) character or CRLF.

Attributes

Source:: character.scala

This parser tries to parse an octal digit, and returns it if successful.

An octal digit is one of '0' to '7' (inclusive).

Attributes

See also:: isOctDigit
Source:: character.scala

This parser tries to parse a space or tab character, and returns it if successful

Attributes

See also:: isSpace
Source:: character.scala

This parser tries to parse a tab ('\t') character, and returns it if successful.

This parser does not recognise vertical tabs, only horizontal ones.

Attributes

Source:: character.scala

This parser tries to parse an uppercase letter, and returns it if successful.

An uppercase letter is any character c <= '\uFFFF' whose Unicode Category Type is Uppercase Letter (Lu). Examples of characters within this category include:

the Latin letters 'A' through 'Z'
Latin special character such as 'Å', 'Ç', 'Õ'
Cryillic letters
Greek letters
Coptic letters

The full list of codepoints found in a category can be found in the Unicode Character Database.

Attributes

Source:: character.scala

This parser tries to parse a whitespace character, and returns it if successful.

A whitespace character is one of:

a space (' ')
a tab ('\t')
a line feed ('\n')
a carriage return ('\r')
a form feed ('\f')
a vertical tab ('\u000B')

Attributes

See also:: isWhitespace
Source:: character.scala

Whitespace Skipping Parsers

These parsers are designed to skip chunks of whitespace, for very rudimentary lexing tasks. It is probably better to use the functionality of parsley.token.

This parser skips zero or more space characters using space.

Attributes

See also:: combinator.skipMany
Source:: character.scala

This parser skips zero or more space characters using whitespace.

Attributes

See also:: combinator.skipMany
Source:: character.scala

Character Predicates

These are useful for providing to the sub-descriptions of a token.descriptions.LexicalDesc to specify behaviour for the lexer. Other than that, they aren't particularly useful.