the type of input elements the provided parsers consume (When consuming invidual characters, a parser is typically called a scanner, which produces tokens that are consumed by what is normally called a parser.
the type of input elements the provided parsers consume (When consuming invidual characters, a parser is typically called a scanner, which produces tokens that are consumed by what is normally called a parser. Nonetheless, the same principles apply, regardless of the input type.)
The fatal failure case of ParseResult: contains an error-message and the remaining input.
The failure case of ParseResult
: contains an error-message and the remaining input.
The parser input is an abstract reader of input elements, i.
The parser input is an abstract reader of input elements, i.e. the type of input the parsers in this component expect.
A common super-class for unsuccessful parse results.
A parser whose ~
combinator disallows back-tracking.
The root class of packrat parsers.
A specialized Reader
class that wraps an underlying Reader
and provides memoization of parse results.
A base class for parser results.
The root class of parsers.
The success case of ParseResult
: contains the result and the remaining input.
A wrapper over sequence of matches.
An extractor so NoSuccess(msg, next)
can be used in matches.
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)
a description of the kind of element this parser expects (for error messages)
a partial function that determines when this parser is successful and what its output is
A parser that succeeds if f
is applicable to the first element of the input,
applying f
to it to produce the result.
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
.
the list of expected elements
a Parser that recognizes a specified list of elements
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 Token
s, Identifier("new")
(which is a Token
) can be used directly,
instead of first creating a Parser
using accept(Identifier("new"))
.
the Elem
that must be the next piece of input for the returned parser to succeed
a tParser
that succeeds if e
is the next available input.
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.
A predicate that determines which elements match.
A function from the received element into an error message.
A parser for elements satisfying p(e).
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)
a description of the kind of element this parser expects (for error messages)
a partial function that determines when this parser is successful and what its output is
A parser that succeeds if f
is applicable to the first element of the input,
applying f
to it to produce the result.
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
.
the list of expected elements
a Parser that recognizes a specified list of elements
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.
a parser that parses the first element
a parser that parses the subsequent elements
a parser that parses the token(s) separating the elements, yielding a left-associative function that combines two elements into one
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.
a parser that parses the elements
a parser that parses the token(s) separating the elements, yielding a left-associative function that combines two elements into one
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.
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)
a parser that parses the elements
a parser that parses the token(s) separating the elements, yielding a right-associative function that combines two elements into one
the "last" (left-most) combination function to be applied
the "first" (right-most) element to be combined
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).
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
.
the Elem
that must be the next piece of input for the returned parser to succeed
a Parser
that succeeds if e
is the next available input (and returns it).
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.
The element kind, used for error messages
A predicate that determines which elements match.
A parser that results in an error.
A parser that results in an error.
The error message describing the failure.
A parser that always fails with the specified error message.
A parser that always fails.
A parser that always fails.
The error message describing the failure.
A parser that always fails with the specified error message.
A parser generator for guard expressions.
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
that is to be applied to the input
A parser that returns success if and only if p
succeeds but
never consumes any input
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.
Explicitly convert a given parser to a memoizing packrat parser.
Explicitly convert a given parser to a memoizing packrat parser.
In most cases, client code should avoid calling memo
directly
and rely on implicit conversion instead.
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
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.
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.
A Parser
that is tried on the input
a Parser
that always succeeds: either with the result provided by p
or
with the empty result
Implicitly convert a parser to a packrat parser.
Implicitly convert a parser to a packrat parser. The conversion is triggered by giving the appropriate target type:
val myParser: PackratParser[MyResult] = aParser
A parser generator delimiting whole phrases (i.
A parser generator delimiting whole phrases (i.e. programs).
Overridden to make sure any input passed to the argument parser
is wrapped in a PackratReader
.
the parser that must consume all input for the resulting parser to succeed.
a parser that has the same result as p
, but that only succeeds
if p
consumed all the input.
positioned
decorates a parser's result with the start position of the
input it consumed.
positioned
decorates a parser's result with the start position of the
input it consumed.
a Parser
whose result conforms to Positional
.
A parser that has the same behaviour as p
, but which marks its
result with the start position of the input it consumed,
if it didn't already have a position.
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
).
a Parser
that is to be applied successively to the input
A parser that returns a list of results produced by repeatedly applying p
to the input.
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
)
a Parser
that parses the first piece of input
a Parser
that is to be applied successively to the rest of the input (if any) -- evaluated at most once, and only when necessary
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).
(Changed in version 2.9.0) The p0
call-by-name arguments is evaluated at most once per constructed Parser object, instead of on every need that arises during parsing.
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
)
a Parser
that is to be applied successively to the input
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).
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.
a Parser
that is to be applied successively to the input
a Parser
that parses the elements that separate the elements parsed by p
(interleaved with q
)
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.
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
).
the exact number of times p
must succeed
a Parser
that is to be applied successively to the input
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).
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.
a Parser
that is to be applied successively to the input
a Parser
that parses the elements that separate the elements parsed by p
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.
A parser that always succeeds.
A parser that always succeeds.
The result for the parser
A parser that always succeeds, with the given result v
PackratParsers
is a component that extends the parser combinators provided by scala.util.parsing.combinator.Parsers with a memoization facility (Packrat Parsing).Packrat Parsing is a technique for implementing backtracking, recursive-descent parsers, with the advantage that it guarantees unlimited lookahead and a linear parse time. Using this technique, left recursive grammars can also be accepted.
Using
PackratParsers
is very similar to usingParsers
:Parsers
(directly or through a subclass) can mix inPackratParsers
. Example:object MyGrammar extends StandardTokenParsers with PackratParsers
def
without formal parameters becomes alazy val
, and its type is changed fromParser[Elem]
toPackratParser[Elem]
. So, for example,def production: Parser[Int] = {...}
becomeslazy val production: PackratParser[Int] = {...}
PackratParser
s is not an all or nothing decision. They can be free mixed with regularParser
s in a single grammar.Cached parse results are attached to the input, not the grammar. Therefore,
PackratsParser
s require aPackratReader
as input, which adds memoization to an underlyingReader
. Programmers can createPackratReader
objects either manually, as inproduction(new PackratReader(new lexical.Scanner("input")))
, but the common way should be to rely on the combinatorphrase
to wrap a given input with aPackratReader
if the input is not one itself.2.8
Alessandro Warth, James R. Douglass, Todd Millstein: "Packrat Parsers Can Support Left Recursion." PEPM'08
Bryan Ford: "Packrat Parsing: Simple, Powerful, Lazy, Linear Time." ICFP'02