Class Parser.Rule<T>

java.lang.Object

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

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

All Implemented Interfaces:

Production<T>

Enclosing class:

Parser<T>

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

A forward-declared production 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.

To prevent StackOverflowError, rules enforce a maximum recursion depth limit. The recursion depth is tracked globally per parse operation across all recursive rules on the call stack. Each rule enforces its own limit against this global depth.

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()	Creates a rule with a default maximum recursion depth of 100.
Rule(int maxRecursionDepth)	Creates a rule with the given maximum recursion depth.

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, anyOf, anyOf, atLeastOnce, atLeastOnce, atLeastOnce, atLeastOnceDelimitedBy, atLeastOnceDelimitedBy, atLeastOnceDelimitedBy, atLeastOnceDelimitedBy, between, bmpCodeUnit, caseInsensitive, caseInsensitiveWord, chars, consecutive, consecutive, consecutive, define, digits, digits, first, flatMap, followedBy, followedBy, followedByOrEof, hexDigits, isPrefixOf, literally, literally, map, mapWithIndex, matches, nestedBy, nestedByWithEscapes, notFollowedBy, notFollowedBy, notFollowedByEof, notImmediatelyFollowedBy, one, one, one, one, optional, optionallyFollowedBy, optionallyFollowedBy, optionallyFollowedBy, optionallyFollowedBy, or, or, or, orElse, parse, parse, parseSkipping, parseSkipping, parseToStream, parseToStream, parseToStream, probe, probe, probe, quotedBy, quotedBy, quotedByWithEscapes, quotedByWithEscapes, sequence, sequence, sequence, sequence, sequence, sequence, sequence, skipping, skipping, source, string, suchThat, then, then, thenReturn, withPostfixes, withPostfixes, withPostfixes, withPrefixes, word, word, zeroOrMore, zeroOrMore, zeroOrMore, zeroOrMore, zeroOrMore, zeroOrMoreDelimited, zeroOrMoreDelimitedBy, zeroOrMoreDelimitedBy, zeroOrMoreDelimitedBy

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.google.common.labs.parse.Production

between, between, between, between, followedBy, immediatelyBetween

Constructor Details

Rule

public Rule()

Creates a rule with a default maximum recursion depth of 100.

Rule

public Rule(int maxRecursionDepth)

Creates a rule with the given maximum recursion depth.

The recursion depth is tracked globally per parse operation across all recursive rules on the call stack.

Throws:

IllegalArgumentException - if maxRecursionDepth is not positive.

Since:

10.6

Method Details

definedAs

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

Define this rule as parser and returns it.