scala-parser-combinators/scala.util.parsing.combinator/Parsers/Parser

Parser

abstract class Parser[+T] extends Input => ParseResult[T]
The root class of parsers.
Parsers are functions from the Input type to ParseResult.
trait Input => ParseResult[T]
class Object
trait Matchable
class Any
trait OnceParser[T]

Value members

Methods

def named(n: String): Parser
override def toString: String
Definition Classes
Function1 -> Any
def apply(in: Input): ParseResult[T]
An unspecified method that defines the behaviour of this parser.
def flatMap[U](f: T => Parser[U]): Parser[U]
def map[U](f: T => U): Parser[U]
def filter(p: T => Boolean): Parser[T]
def withFilter(p: T => Boolean): Parser[T]
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def append[U >: T](p0: => Parser[U]): Parser[U]
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def ~[U](q: => Parser[U]): Parser[T ~ U]
A parser combinator for sequential composition.
p ~ q succeeds if p succeeds and q succeeds on the input left over by p.
Value Params
q
a parser that will be executed after p (this parser)
succeeds -- evaluated at most once, and only when necessary.
Returns
a Parser that -- on success -- returns a ~ (like a Pair,
but easier to pattern match on) that contains the result of p and
that of q. The resulting parser fails if either p or q fails.
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def ~>[U](q: => Parser[U]): Parser[U]
A parser combinator for sequential composition which keeps only the right result.
p ~> q succeeds if p succeeds and q succeeds on the input left over by p.
Value Params
q
a parser that will be executed after p (this parser)
succeeds -- evaluated at most once, and only when necessary.
Returns
a Parser that -- on success -- returns the result of q.
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def <~[U](q: => Parser[U]): Parser[T]
A parser combinator for sequential composition which keeps only the left result.
p <~ q succeeds if p succeeds and q succeeds on the input
left over by p.
Value Params
q
a parser that will be executed after p (this parser) succeeds -- evaluated at most once, and only when necessary
Returns
a Parser that -- on success -- returns the result of p.
Note
<~ has lower operator precedence than ~ or ~>.
def -[U](q: Parser[U]): Parser[T]
A parser combinator for exceptions.
p - q succeeds if p succeeds, and q fails on the same input given p.
Value Params
q
a parser that will be executed before p (this parser). q will not consume the input.
Returns
a Parser that returns the result of p (this parser) if it succeeds and q fails. If q succeeds, the parser will fail.
def ~![U](p: => Parser[U]): Parser[T ~ U]
A parser combinator for non-back-tracking sequential composition.
p ~! q succeeds if p succeeds and q succeeds on the input left over by p.
In case of failure, no back-tracking is performed (in an earlier parser produced by the | combinator).
Value Params
p
a parser that will be executed after p (this parser) succeeds
Returns
a Parser that -- on success -- returns a ~ (like a Pair, but easier to pattern match on)
that contains the result of p and that of q.
The resulting parser fails if either p or q fails, this failure is fatal.
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def ~>![U](q: => Parser[U]): Parser[U]
A parser combinator for non-back-tracking sequential composition which only keeps the right result.
p ~>! q succeeds if p succeds and q succeds on the input left over by p.
In case of failure, no back-tracking is performed (in an earlier parser produced by the | combinator).
Value Params
q
a parser that will be executed after p (this parser) succeeds -- evaluated at most once, and only when necessary
Returns
a Parser that -- on success -- reutrns the result of q.
The resulting parser fails if either p or q fails, this failure is fatal.
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def <~![U](q: => Parser[U]): Parser[T]
A parser combinator for non-back-tracking sequential composition which only keeps the left result.
p <~! q succeeds if p succeds and q succeds on the input left over by p.
In case of failure, no back-tracking is performed (in an earlier parser produced by the | combinator).
Value Params
q
a parser that will be executed after p (this parser) succeeds -- evaluated at most once, and only when necessary
Returns
a Parser that -- on success -- reutrns the result of p.
The resulting parser fails if either p or q fails, this failure is fatal.
def |[U >: T](q: => Parser[U]): Parser[U]
A parser combinator for alternative composition.
p | q succeeds if p succeeds or q succeeds.
Note that q is only tried if ps failure is non-fatal (i.e., back-tracking is allowed).
Value Params
q
a parser that will be executed if p (this parser) fails (and allows back-tracking)
Returns
a Parser that returns the result of the first parser to succeed (out of p and q)
The resulting parser succeeds if (and only if)
- p succeeds, ''or''
- if p fails allowing back-tracking and q succeeds.
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def |||[U >: T](q0: => Parser[U]): Parser[U]
A parser combinator for alternative with longest match composition.
p ||| q succeeds if p succeeds or q succeeds.
If p and q both succeed, the parser that consumed the most characters accepts.
Value Params
q0
a parser that accepts if p consumes less characters. -- evaluated at most once, and only when necessary
Returns
a Parser that returns the result of the parser consuming the most characters (out of p and q).
def ^^[U](f: T => U): Parser[U]
A parser combinator for function application.
p ^^ f succeeds if p succeeds; it returns f applied to the result of p.
Value Params
f
a function that will be applied to this parser's result (see map in ParseResult).
Returns
a parser that has the same behaviour as the current parser, but whose result is
transformed by f.
@migration("The call-by-name argument is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.", "2.9.0")
def ^^^[U](v: => U): Parser[U]
A parser combinator that changes a successful result into the specified value.
p ^^^ v succeeds if p succeeds; discards its result, and returns v instead.
Value Params
v
The new result for the parser, evaluated at most once (if p succeeds), not evaluated at all if p fails.
Returns
a parser that has the same behaviour as the current parser, but whose successful result is v
def ^?[U](f: PartialFunction[T, U], error: T => String): Parser[U]
A parser combinator for partial function application.
p ^? (f, error) succeeds if p succeeds AND f is defined at the result of p;
in that case, it returns f applied to the result of p. If f is not applicable,
error(the result of p) should explain why.
Value Params
error
a function that takes the same argument as f and produces an error message
to explain why f wasn't applicable
f
a partial function that will be applied to this parser's result
(see mapPartial in ParseResult).
Returns
a parser that succeeds if the current parser succeeds and f is applicable
to the result. If so, the result will be transformed by f.
def ^?[U](f: PartialFunction[T, U]): Parser[U]
A parser combinator for partial function application.
p ^? f succeeds if p succeeds AND f is defined at the result of p;
in that case, it returns f applied to the result of p.
Value Params
f
a partial function that will be applied to this parser's result
(see mapPartial in ParseResult).
Returns
a parser that succeeds if the current parser succeeds and f is applicable
to the result. If so, the result will be transformed by f.
def into[U](fq: T => Parser[U]): Parser[U]
A parser combinator that parameterizes a subsequent parser with the
result of this one.
Use this combinator when a parser depends on the result of a previous
parser. p should be a function that takes the result from the first
parser and returns the second parser.
p into fq (with fq typically {x => q}) first applies p, and
then, if p successfully returned result r, applies fq(r) to the
rest of the input.
''From: G. Hutton. Higher-order functions for parsing. J. Funct. Program., 2(3):323--343, 1992.''
Value Params
fq
a function that, given the result from this parser, returns
the second parser to be applied
Returns
a parser that succeeds if this parser succeeds (with result x)
and if then fq(x) succeeds
Example
{{{
def perlRE = "m" ~> (".".r into (separator => """[^%s] *""".format(separator).r <~ separator))
}}}
def >>[U](fq: T => Parser[U]): Parser[U]
Returns into(fq).
def *: Parser[List[T]]
Returns a parser that repeatedly parses what this parser parses.
Returns
rep(this)
def *[U >: T](sep: => Parser[(U, U) => U]): Parser[U]
Returns a parser that repeatedly parses what this parser parses,
interleaved with the sep parser. The sep parser specifies how
the results parsed by this parser should be combined.
Returns
chainl1(this, sep)
def +: Parser[List[T]]
Returns a parser that repeatedly (at least once) parses what this parser parses.
Returns
rep1(this)
def ?: Parser[Option[T]]
Returns a parser that optionally parses what this parser parses.
Returns
opt(this)
def withFailureMessage(msg: String): Parser[T]
Changes the failure message produced by a parser.
This doesn't change the behavior of a parser on neither
success nor error, just on failure. The semantics are
slightly different than those obtained by doing | failure(msg),
in that the message produced by this method will always
replace the message produced, which is not guaranteed
by that idiom.
For example, parser p below will always produce the
designated failure message, while q will not produce
it if sign is parsed but number is not.
{{{
def p = sign.? ~ number withFailureMessage "Number expected!"
def q = sign.? ~ number | failure("Number expected!")
}}}
Value Params
msg
The message that will replace the default failure message.
Returns
A parser with the same properties and different failure message.
def withErrorMessage(msg: String): Parser[T]
Changes the error message produced by a parser.
This doesn't change the behavior of a parser on neither
success nor failure, just on error. The semantics are
slightly different than those obtained by doing | error(msg),
in that the message produced by this method will always
replace the message produced, which is not guaranteed
by that idiom.
For example, parser p below will always produce the
designated error message, while q will not produce
it if sign is parsed but number is not.
{{{
def p = sign.? ~ number withErrorMessage "Number expected!"
def q = sign.? ~ number | error("Number expected!")
}}}
Value Params
msg
The message that will replace the default error message.
Returns
A parser with the same properties and different error message.

Inherited methods

@unspecialized
def andThen[A](g: R => A): T1 => A
Inhertied from
Function1
@unspecialized
def compose[A](g: A => T1): A => R
Inhertied from
Function1