Class Parser.Rule<T>

java.lang.Object

com.google.common.labs.parse.Parser<T>

com.google.common.labs.parse.Parser.Rule<T>

Enclosing class:

Parser<T>

public static final class Parser.Rule<T>
extends Parser<T>

A forward-declared grammar rule, to be used for recursive grammars.

For example, to create a parser for a simple calculator that supports single-digit numbers, addition, and parentheses, you can write:

 var rule = new Parser.Rule<Integer>();
 Parser<Integer> num = Parser.single(CharPredicate.inRange('0', '9')).map(c -> c - '0');
 Parser<Integer> atomic = rule.between("(", ")").or(num);
 Parser<Integer> expr =
     atomic.atLeastOnceDelimitedBy("+")
         .map(nums -> nums.stream().mapToInt(n -> n).sum());
 return rule.definedAs(expr);
 

For simple definitions, you could use the Parser.define(java.util.function.Function<? super com.google.common.labs.parse.Parser<T>, ? extends com.google.common.labs.parse.Parser<? extends T>>) method with a lambda to elide the need of an explicit forward declaration.

Nested Class Summary

Nested classes/interfaces inherited from class com.google.common.labs.parse.Parser

Parser.Lexical, Parser.OrEmpty, Parser.ParseException, Parser.Rule<T>

Constructor Summary

Constructors

Constructor	Description
Rule()

Method Summary

Modifier and Type	Method	Description
<S extends T> Parser<S>	definedAs(Parser<S> parser)	Define this rule as parser and returns it.

Methods inherited from class com.google.common.labs.parse.Parser

anyOf, atLeastOnce, atLeastOnce, atLeastOnce, atLeastOnceDelimitedBy, atLeastOnceDelimitedBy, atLeastOnceDelimitedBy, between, between, chars, consecutive, consecutive, define, digits, flatMap, followedBy, followedBy, followedBy, followedByOrEof, immediatelyBetween, literally, literally, map, notFollowedBy, notFollowedBy, notImmediatelyFollowedBy, optional, optionallyFollowedBy, optionallyFollowedBy, or, or, or, orElse, parse, parse, parseSkipping, parseSkipping, parseToStream, parseToStream, parseToStream, postfix, prefix, probe, probe, probe, quotedStringWithEscapes, sequence, sequence, sequence, single, skipping, skipping, source, string, suchThat, then, then, thenReturn, word, zeroOrMore, zeroOrMore, zeroOrMore, zeroOrMoreDelimited, zeroOrMoreDelimited, zeroOrMoreDelimitedBy, zeroOrMoreDelimitedBy

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Rule

public Rule()

Method Details

definedAs

public <S extends T> Parser<S> definedAs(Parser<S> parser)

Define this rule as parser and returns it.