scala-parser-combinators/scala.util.parsing.combinator/RegexParsers

RegexParsers

trait RegexParsers extends Parsers

The ''most important'' differences between RegexParsers and scala.util.parsing.combinator.Parsers are:

The ''most important'' differences between RegexParsers and scala.util.parsing.combinator.Parsers are:

  • Elem is defined to be scala.Char
  • There's an implicit conversion from java.lang.String to Parser[String], so that string literals can be used as parser combinators.
  • There's an implicit conversion from scala.util.matching.Regex to Parser[String], so that regex expressions can be used as parser combinators.
  • The parsing methods call the method skipWhitespace (defaults to true) and, if true, skip any whitespace before each parser is called.
  • Protected val whiteSpace returns a regex that identifies whitespace.

For example, this creates a very simple calculator receiving String input:

object Calculator extends RegexParsers {
  def number: Parser[Double] = """\d+(\.\d*)?""".r ^^ { _.toDouble }
  def factor: Parser[Double] = number | "(" ~> expr <~ ")"
  def term  : Parser[Double] = factor ~ rep( "*" ~ factor | "/" ~ factor) ^^ {
    case number ~ list => list.foldLeft(number) {
      case (x, "*" ~ y) => x * y
      case (x, "/" ~ y) => x / y
    }
  }
  def expr  : Parser[Double] = term ~ rep("+" ~ log(term)("Plus term") | "-" ~ log(term)("Minus term")) ^^ {
    case number ~ list => list.foldLeft(number) {
      case (x, "+" ~ y) => x + y
      case (x, "-" ~ y) => x - y
    }
  }

  def apply(input: String): Double = parseAll(expr, input) match {
    case Success(result, _) => result
    case failure : NoSuccess => scala.sys.error(failure.msg)
  }
}
trait Parsers
class Object
trait Matchable
class Any

Type members

Inherited classlikes

case class Error(msg: String, next: Input)

The fatal failure case of ParseResult: contains an error-message and the remaining input. No back-tracking is done when a parser returns an Error.

The fatal failure case of ParseResult: contains an error-message and the remaining input. No back-tracking is done when a parser returns an Error.

Value Params
msg

An error message string describing the error.

next

The parser's unconsumed input at the point where the error occurred.

Inherited from
Parsers
case class Failure(msg: String, next: Input)

The failure case of ParseResult: contains an error-message and the remaining input. Parsing will back-track when a failure occurs.

The failure case of ParseResult: contains an error-message and the remaining input. Parsing will back-track when a failure occurs.

Value Params
msg

An error message string describing the failure.

next

The parser's unconsumed input at the point where the failure occurred.

Inherited from
Parsers
object NoSuccess

An extractor so NoSuccess(msg, next) can be used in matches.

An extractor so NoSuccess(msg, next) can be used in matches.

Inherited from
Parsers
sealed abstract class NoSuccess(val msg: String, val next: Input)

A common super-class for unsuccessful parse results.

A common super-class for unsuccessful parse results.

Inherited from
Parsers
trait OnceParser[+T]

A parser whose ~ combinator disallows back-tracking.

A parser whose ~ combinator disallows back-tracking.

Inherited from
Parsers
sealed abstract class ParseResult[+T]

A base class for parser results. A result is either successful or not (failure may be fatal, i.e., an Error, or not, i.e., a Failure). On success, provides a result of type T which consists of some result (and the rest of the input).

A base class for parser results. A result is either successful or not (failure may be fatal, i.e., an Error, or not, i.e., a Failure). On success, provides a result of type T which consists of some result (and the rest of the input).

Inherited from
Parsers
abstract class Parser[+T]

The root class of parsers. Parsers are functions from the Input type to ParseResult.

The root class of parsers. Parsers are functions from the Input type to ParseResult.

Inherited from
Parsers
case class Success[+T](result: T, next: Input)

The success case of ParseResult: contains the result and the remaining input.

The success case of ParseResult: contains the result and the remaining input.

Value Params
next

The parser's remaining input

result

The parser's output

Inherited from
Parsers
case class ~[+a, +b](_1: a, _2: b)

A wrapper over sequence of matches.

A wrapper over sequence of matches.

Given p1: Parser[A] and p2: Parser[B], a parser composed with p1 ~ p2 will have type Parser[~[A, B]]. The successful result of the parser can be extracted from this case class.

It also enables pattern matching, so something like this is possible:

def concat(p1: Parser[String], p2: Parser[String]): Parser[String] =
  p1 ~ p2 ^^ { case a ~ b => a + b }
Inherited from
Parsers

Types

type Elem = Char

Inherited types

type Input = Reader[Elem]

The parser input is an abstract reader of input elements, i.e. the type of input the parsers in this component expect.

The parser input is an abstract reader of input elements, i.e. the type of input the parsers in this component expect.

Inherited from
Parsers

Value members

Concrete methods

override def err(msg: String): Parser[Nothing]

A parser that results in an error.

A parser that results in an error.

This parser additionally skips whitespace if skipWhitespace returns true.

Definition Classes
protected def handleWhiteSpace(source: CharSequence, offset: Int): Int

Method called to handle whitespace before parsers.

Method called to handle whitespace before parsers.

It checks skipWhitespace and, if true, skips anything matching whiteSpace starting from the current offset.

Value Params
offset

The offset into source from which to match.

source

The input being parsed.

Returns

The offset to be used for the next parser.

def parse[T](p: Parser[T], in: Reader[Char]): ParseResult[T]

Parse some prefix of reader in with parser p.

Parse some prefix of reader in with parser p.

def parse[T](p: Parser[T], in: CharSequence): ParseResult[T]

Parse some prefix of character sequence in with parser p.

Parse some prefix of character sequence in with parser p.

def parse[T](p: Parser[T], in: Reader): ParseResult[T]

Parse some prefix of reader in with parser p.

Parse some prefix of reader in with parser p.

def parseAll[T](p: Parser[T], in: Reader[Char]): ParseResult[T]

Parse all of reader in with parser p.

Parse all of reader in with parser p.

def parseAll[T](p: Parser[T], in: Reader): ParseResult[T]

Parse all of reader in with parser p.

Parse all of reader in with parser p.

def parseAll[T](p: Parser[T], in: CharSequence): ParseResult[T]

Parse all of character sequence in with parser p.

Parse all of character sequence in with parser p.

override def phrase[T](p: Parser[T]): Parser[T]

A parser generator delimiting whole phrases (i.e. programs).

A parser generator delimiting whole phrases (i.e. programs).

phrase(p) succeeds if p succeeds and no input is left over after p.

Value Params
p

the parser that must consume all input for the resulting parser to succeed.

Returns

a parser that has the same result as p, but that only succeeds if p consumed all the input.

Definition Classes
override def positioned[T <: Positional](p: => Parser[T]): Parser[T]

positioned decorates a parser's result with the start position of the input it consumed. If whitespace is being skipped, then it is skipped before the start position is recorded.

positioned decorates a parser's result with the start position of the input it consumed. If whitespace is being skipped, then it is skipped before the start position is recorded.

Value Params
p

a Parser whose result conforms to Positional.

Returns

A parser that has the same behaviour as p, but which marks its result with the start position of the input it consumed after whitespace has been skipped, if it didn't already have a position.

Definition Classes
def skipWhitespace: Boolean

Inherited methods

def OnceParser[T](f: Input => ParseResult[T]): Parser[T] & OnceParser[T]
Inherited from
Parsers
def Parser[T](f: Input => ParseResult[T]): Parser[T]
Inherited from
Parsers
def accept[U](expected: String, f: PartialFunction[Elem, U]): Parser[U]

The parser that matches an element in the domain of the partial function f.

The parser that matches an element in the domain of the partial function f.

If f is defined on the first element in the input, f is applied to it to produce this parser's result.

Example: The parser accept("name", {case Identifier(n) => Name(n)}) accepts an Identifier(n) and returns a Name(n)

Value Params
expected

a description of the kind of element this parser expects (for error messages)

f

a partial function that determines when this parser is successful and what its output is

Returns

A parser that succeeds if f is applicable to the first element of the input, applying f to it to produce the result.

Inherited from
Parsers
def accept[ES](es: ES)(f: ES => List[Elem]): Parser[List[Elem]]

A parser that matches only the given list of element es.

A parser that matches only the given list of element es.

accept(es) succeeds if the input subsequently provides the elements in the list es.

Value Params
es

the list of expected elements

Returns

a Parser that recognizes a specified list of elements

Inherited from
Parsers
def acceptIf(p: Elem => Boolean)(err: Elem => String): Parser[Elem]

A parser matching input elements that satisfy a given predicate.

A parser matching input elements that satisfy a given predicate.

acceptIf(p)(el => "Unexpected "+el) succeeds if the input starts with an element e for which p(e) is true.

Value Params
err

A function from the received element into an error message.

p

A predicate that determines which elements match.

Returns

A parser for elements satisfying p(e).

Inherited from
Parsers
def acceptMatch[U](expected: String, f: PartialFunction[Elem, U]): Parser[U]

The parser that matches an element in the domain of the partial function f.

The parser that matches an element in the domain of the partial function f.

If f is defined on the first element in the input, f is applied to it to produce this parser's result.

Example: The parser acceptMatch("name", {case Identifier(n) => Name(n)}) accepts an Identifier(n) and returns a Name(n)

Value Params
expected

a description of the kind of element this parser expects (for error messages)

f

a partial function that determines when this parser is successful and what its output is

Returns

A parser that succeeds if f is applicable to the first element of the input, applying f to it to produce the result.

Inherited from
Parsers
def acceptSeq[ES](es: ES)(f: ES => Iterable[Elem]): Parser[List[Elem]]

A parser that matches only the given scala.collection.Iterable collection of elements es.

A parser that matches only the given scala.collection.Iterable collection of elements es.

acceptSeq(es) succeeds if the input subsequently provides the elements in the iterable es.

Value Params
es

the list of expected elements

Returns

a Parser that recognizes a specified list of elements

Inherited from
Parsers
def chainl1[T, U](first: => Parser[T], p: => Parser[U], q: => Parser[(T, U) => T]): Parser[T]

A parser generator that, roughly, generalises the rep1sep generator so that q, which parses the separator, produces a left-associative function that combines the elements it separates.

A parser generator that, roughly, generalises the rep1sep generator so that q, which parses the separator, produces a left-associative function that combines the elements it separates.

Value Params
first

a parser that parses the first element

p

a parser that parses the subsequent elements

q

a parser that parses the token(s) separating the elements, yielding a left-associative function that combines two elements into one

Inherited from
Parsers
def chainl1[T](p: => Parser[T], q: => Parser[(T, T) => T]): Parser[T]

A parser generator that, roughly, generalises the rep1sep generator so that q, which parses the separator, produces a left-associative function that combines the elements it separates.

A parser generator that, roughly, generalises the rep1sep generator so that q, which parses the separator, produces a left-associative function that combines the elements it separates.

''From: J. Fokker. Functional parsers. In J. Jeuring and E. Meijer, editors, Advanced Functional Programming, volume 925 of Lecture Notes in Computer Science, pages 1--23. Springer, 1995.''

Value Params
p

a parser that parses the elements

q

a parser that parses the token(s) separating the elements, yielding a left-associative function that combines two elements into one

Inherited from
Parsers
def chainr1[T, U](p: => Parser[T], q: => Parser[(T, U) => U], combine: (T, U) => U, first: U): Parser[U]

A parser generator that generalises the rep1sep generator so that q, which parses the separator, produces a right-associative function that combines the elements it separates. Additionally, the right-most (last) element and the left-most combining function have to be supplied.

A parser generator that generalises the rep1sep generator so that q, which parses the separator, produces a right-associative function that combines the elements it separates. Additionally, the right-most (last) element and the left-most combining function have to be supplied.

rep1sep(p: Parser[T], q) corresponds to chainr1(p, q ^^ cons, cons, Nil) (where val cons = (x: T, y: List[T]) => x :: y)

Value Params
combine

the "last" (left-most) combination function to be applied

first

the "first" (right-most) element to be combined

p

a parser that parses the elements

q

a parser that parses the token(s) separating the elements, yielding a right-associative function that combines two elements into one

Inherited from
Parsers
def commit[T](p: => Parser[T]): Parser[T]

Wrap a parser so that its failures become errors (the | combinator will give up as soon as it encounters an error, on failure it simply tries the next alternative).

Wrap a parser so that its failures become errors (the | combinator will give up as soon as it encounters an error, on failure it simply tries the next alternative).

Inherited from
Parsers
def elem(e: Elem): Parser[Elem]

A parser that matches only the given element e.

A parser that matches only the given element e.

elem(e) succeeds if the input starts with an element e.

Value Params
e

the Elem that must be the next piece of input for the returned parser to succeed

Returns

a Parser that succeeds if e is the next available input (and returns it).

Inherited from
Parsers
def elem(kind: String, p: Elem => Boolean): Parser[Elem]

A parser matching input elements that satisfy a given predicate.

A parser matching input elements that satisfy a given predicate.

elem(kind, p) succeeds if the input starts with an element e for which p(e) is true.

Value Params
kind

The element kind, used for error messages

p

A predicate that determines which elements match.

Inherited from
Parsers
def failure(msg: String): Parser[Nothing]

A parser that always fails.

A parser that always fails.

Value Params
msg

The error message describing the failure.

Returns

A parser that always fails with the specified error message.

Inherited from
Parsers
def guard[T](p: => Parser[T]): Parser[T]

A parser generator for guard expressions. The resulting parser will fail or succeed just like the one given as parameter but it will not consume any input.

A parser generator for guard expressions. The resulting parser will fail or succeed just like the one given as parameter but it will not consume any input.

Value Params
p

a Parser that is to be applied to the input

Returns

A parser that returns success if and only if p succeeds but never consumes any input

Inherited from
Parsers
def log[T](p: => Parser[T])(name: String): Parser[T]

A helper method that turns a Parser into one that will print debugging information to stdout before and after being applied.

A helper method that turns a Parser into one that will print debugging information to stdout before and after being applied.

Inherited from
Parsers
def mkList[T]: T ~ List[T] => List[T]

Given a concatenation with a repetition (list), move the concatenated element into the list

Given a concatenation with a repetition (list), move the concatenated element into the list

Inherited from
Parsers
def not[T](p: => Parser[T]): Parser[Unit]

Wrap a parser so that its failures and errors become success and vice versa -- it never consumes any input.

Wrap a parser so that its failures and errors become success and vice versa -- it never consumes any input.

Inherited from
Parsers
def opt[T](p: => Parser[T]): Parser[Option[T]]

A parser generator for optional sub-phrases.

A parser generator for optional sub-phrases.

opt(p) is a parser that returns Some(x) if p returns x and None if p fails.

Value Params
p

A Parser that is tried on the input

Returns

a Parser that always succeeds: either with the result provided by p or with the empty result

Inherited from
Parsers
def rep[T](p: => Parser[T]): Parser[List[T]]

A parser generator for repetitions.

A parser generator for repetitions.

rep(p) repeatedly uses p to parse the input until p fails (the result is a List of the consecutive results of p).

Value Params
p

a Parser that is to be applied successively to the input

Returns

A parser that returns a list of results produced by repeatedly applying p to the input.

Inherited from
Parsers
@migration("The `p0` call-by-name arguments is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def rep1[T](first: => Parser[T], p0: => Parser[T]): Parser[List[T]]

A parser generator for non-empty repetitions.

A parser generator for non-empty repetitions.

rep1(f, p) first uses f (which must succeed) and then repeatedly uses p to parse the input until p fails (the result is a List of the consecutive results of f and p)

Value Params
first

a Parser that parses the first piece of input

p0

a Parser that is to be applied successively to the rest of the input (if any) -- evaluated at most once, and only when necessary

Returns

A parser that returns a list of results produced by first applying f and then repeatedly p to the input (it only succeeds if f matches).

Inherited from
Parsers
def rep1[T](p: => Parser[T]): Parser[List[T]]

A parser generator for non-empty repetitions.

A parser generator for non-empty repetitions.

rep1(p) repeatedly uses p to parse the input until p fails -- p must succeed at least once (the result is a List of the consecutive results of p)

Value Params
p

a Parser that is to be applied successively to the input

Returns

A parser that returns a list of results produced by repeatedly applying p to the input (and that only succeeds if p matches at least once).

Inherited from
Parsers
def rep1sep[T](p: => Parser[T], q: => Parser[Any]): Parser[List[T]]

A parser generator for non-empty repetitions.

A parser generator for non-empty repetitions.

rep1sep(p, q) repeatedly applies p interleaved with q to parse the input, until p fails. The parser p must succeed at least once.

Value Params
p

a Parser that is to be applied successively to the input

q

a Parser that parses the elements that separate the elements parsed by p (interleaved with q)

Returns

A parser that returns a list of results produced by repeatedly applying p to the input (and that only succeeds if p matches at least once). The results of p are collected in a list. The results of q are discarded.

Inherited from
Parsers
def repN[T](num: Int, p: => Parser[T]): Parser[List[T]]

A parser generator for a specified number of repetitions.

A parser generator for a specified number of repetitions.

repN(n, p) uses p exactly n time to parse the input (the result is a List of the n consecutive results of p).

Value Params
num

the exact number of times p must succeed

p

a Parser that is to be applied successively to the input

Returns

A parser that returns a list of results produced by repeatedly applying p to the input (and that only succeeds if p matches exactly n times).

Inherited from
Parsers
def repNM[T](n: Int, m: Int, p: Parser[T], sep: Parser[Any]): Parser[List[T]]

A parser generator for a specified range of repetitions interleaved by a separator.

A parser generator for a specified range of repetitions interleaved by a separator.

repNM(n, m, p, s) uses p at least n times and up to m times, interleaved with separator s, to parse the input (the result is a List of at least n consecutive results of p and up to m results).

Value Params
m

maximum number of repetitions

n

minimum number of repetitions

p

a Parser that is to be applied successively to the input

sep

a Parser that interleaves with p

Returns

A parser that returns a list of results produced by repeatedly applying p interleaved with sep to the input. The list has a size between n and up to m (and that only succeeds if p matches at least n times).

Inherited from
Parsers
def repsep[T](p: => Parser[T], q: => Parser[Any]): Parser[List[T]]

A parser generator for interleaved repetitions.

A parser generator for interleaved repetitions.

repsep(p, q) repeatedly uses p interleaved with q to parse the input, until p fails. (The result is a List of the results of p.)

Example: repsep(term, ",") parses a comma-separated list of term's, yielding a list of these terms.

Value Params
p

a Parser that is to be applied successively to the input

q

a Parser that parses the elements that separate the elements parsed by p

Returns

A parser that returns a list of results produced by repeatedly applying p (interleaved with q) to the input. The results of p are collected in a list. The results of q are discarded.

Inherited from
Parsers
def success[T](v: T): Parser[T]

A parser that always succeeds.

A parser that always succeeds.

Value Params
v

The result for the parser

Returns

A parser that always succeeds, with the given result v

Inherited from
Parsers

Concrete fields

protected val whiteSpace: Regex

Implicits

Implicits

implicit def literal(s: String): Parser[String]

A parser that matches a literal string

A parser that matches a literal string

implicit def regex(r: Regex): Parser[String]

A parser that matches a regex string

A parser that matches a regex string

Inherited implicits

implicit def accept(e: Elem): Parser[Elem]

A parser that matches only the given element e.

A parser that matches only the given element e.

The method is implicit so that elements can automatically be lifted to their parsers. For example, when parsing Tokens, Identifier("new") (which is a Token) can be used directly, instead of first creating a Parser using accept(Identifier("new")).

Value Params
e

the Elem that must be the next piece of input for the returned parser to succeed

Returns

a tParser that succeeds if e is the next available input.

Inherited from
Parsers