org.antlr.analysis

Class SemanticContext

java.lang.Object

org.antlr.analysis.SemanticContext

Direct Known Subclasses:

SemanticContext.AND, SemanticContext.NOT, SemanticContext.OR, SemanticContext.Predicate

public abstract class SemanticContext
extends Object

A binary tree structure used to record the semantic context in which an NFA configuration is valid. It's either a single predicate or a tree representing an operation tree such as: p1&&p2 or p1||p2. For NFA o-p1->o-p2->o, create tree AND(p1,p2). For NFA (1)-p1->(2) | ^ | | (3)-p2---- we will have to combine p1 and p2 into DFA state as we will be adding NFA configurations for state 2 with two predicates p1,p2. So, set context for combined NFA config for state 2: OR(p1,p2). I have scoped the AND, NOT, OR, and Predicate subclasses of SemanticContext within the scope of this outer class. July 7, 2006: TJP altered OR to be set of operands. the Binary tree made it really hard to reduce complicated || sequences to their minimum. Got huge repeated || conditions.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SemanticContext.AND
static class	SemanticContext.NOT
static class	SemanticContext.OR
static class	SemanticContext.Predicate
static class	SemanticContext.TruePredicate

Field Summary

Fields

Modifier and Type	Field and Description
static SemanticContext	EMPTY_SEMANTIC_CONTEXT Create a default value for the semantic context shared among all NFAConfigurations that do not have an actual semantic context.

Constructor Summary

Constructors

Constructor and Description
SemanticContext()

Method Summary

Methods

Modifier and Type	Method and Description
static SemanticContext	and(SemanticContext a, SemanticContext b)
abstract org.antlr.stringtemplate.StringTemplate	genExpr(CodeGenerator generator, org.antlr.stringtemplate.StringTemplateGroup templates, DFA dfa) Generate an expression that will evaluate the semantic context, given a set of output templates.
abstract SemanticContext	getGatedPredicateContext() Given a semantic context expression tree, return a tree with all nongated predicates set to true and then reduced.
abstract boolean	isSyntacticPredicate()
static SemanticContext	not(SemanticContext a)
static SemanticContext	or(SemanticContext a, SemanticContext b)
void	trackUseOfSyntacticPredicates(Grammar g) Notify the indicated grammar of any syn preds used within this context

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY_SEMANTIC_CONTEXT

public static final SemanticContext EMPTY_SEMANTIC_CONTEXT

Create a default value for the semantic context shared among all NFAConfigurations that do not have an actual semantic context. This prevents lots of if!=null type checks all over; it represents just an empty set of predicates.

Constructor Detail

SemanticContext

public SemanticContext()

Method Detail

getGatedPredicateContext

public abstract SemanticContext getGatedPredicateContext()

Given a semantic context expression tree, return a tree with all nongated predicates set to true and then reduced. So p&&(q||r) would return p&&r if q is nongated but p and r are gated.

genExpr

public abstract org.antlr.stringtemplate.StringTemplate genExpr(CodeGenerator generator,
                                              org.antlr.stringtemplate.StringTemplateGroup templates,
                                              DFA dfa)

Generate an expression that will evaluate the semantic context, given a set of output templates.

isSyntacticPredicate

public abstract boolean isSyntacticPredicate()

trackUseOfSyntacticPredicates

public void trackUseOfSyntacticPredicates(Grammar g)

Notify the indicated grammar of any syn preds used within this context

and

public static SemanticContext and(SemanticContext a,
                  SemanticContext b)

or

public static SemanticContext or(SemanticContext a,
                 SemanticContext b)

not

public static SemanticContext not(SemanticContext a)