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@pboyer @willfaught @parrt @wjkohnen
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// Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
// Use of this file is governed by the BSD 3-clause license that
// can be found in the LICENSE.txt file in the project root.
package antlr
import (
"fmt"
"strconv"
)
// A tree structure used to record the semantic context in which
// an ATN configuration is valid. It's either a single predicate,
// a conjunction {@code p1&&p2}, or a sum of products {@code p1||p2}.
//
// <p>I have scoped the {@link AND}, {@link OR}, and {@link Predicate} subclasses of
// {@link SemanticContext} within the scope of this outer class.</p>
//
type SemanticContext interface {
comparable
evaluate(parser Recognizer, outerContext RuleContext) bool
evalPrecedence(parser Recognizer, outerContext RuleContext) SemanticContext
hash() int
String() string
}
func SemanticContextandContext(a, b SemanticContext) SemanticContext {
if a == nil || a == SemanticContextNone {
return b
}
if b == nil || b == SemanticContextNone {
return a
}
result := NewAND(a, b)
if len(result.opnds) == 1 {
return result.opnds[0]
}
return result
}
func SemanticContextorContext(a, b SemanticContext) SemanticContext {
if a == nil {
return b
}
if b == nil {
return a
}
if a == SemanticContextNone || b == SemanticContextNone {
return SemanticContextNone
}
result := NewOR(a, b)
if len(result.opnds) == 1 {
return result.opnds[0]
}
return result
}
type Predicate struct {
ruleIndex int
predIndex int
isCtxDependent bool
}
func NewPredicate(ruleIndex, predIndex int, isCtxDependent bool) *Predicate {
p := new(Predicate)
p.ruleIndex = ruleIndex
p.predIndex = predIndex
p.isCtxDependent = isCtxDependent // e.g., $i ref in pred
return p
}
//The default {@link SemanticContext}, which is semantically equivalent to
//a predicate of the form {@code {true}?}.
var SemanticContextNone SemanticContext = NewPredicate(-1, -1, false)
func (p *Predicate) evalPrecedence(parser Recognizer, outerContext RuleContext) SemanticContext {
return p
}
func (p *Predicate) evaluate(parser Recognizer, outerContext RuleContext) bool {
var localctx RuleContext
if p.isCtxDependent {
localctx = outerContext
}
return parser.Sempred(localctx, p.ruleIndex, p.predIndex)
}
func (p *Predicate) equals(other interface{}) bool {
if p == other {
return true
} else if _, ok := other.(*Predicate); !ok {
return false
} else {
return p.ruleIndex == other.(*Predicate).ruleIndex &&
p.predIndex == other.(*Predicate).predIndex &&
p.isCtxDependent == other.(*Predicate).isCtxDependent
}
}
func (p *Predicate) hash() int {
return p.ruleIndex*43 + p.predIndex*47
}
func (p *Predicate) String() string {
return "{" + strconv.Itoa(p.ruleIndex) + ":" + strconv.Itoa(p.predIndex) + "}?"
}
type PrecedencePredicate struct {
precedence int
}
func NewPrecedencePredicate(precedence int) *PrecedencePredicate {
p := new(PrecedencePredicate)
p.precedence = precedence
return p
}
func (p *PrecedencePredicate) evaluate(parser Recognizer, outerContext RuleContext) bool {
return parser.Precpred(outerContext, p.precedence)
}
func (p *PrecedencePredicate) evalPrecedence(parser Recognizer, outerContext RuleContext) SemanticContext {
if parser.Precpred(outerContext, p.precedence) {
return SemanticContextNone
}
return nil
}
func (p *PrecedencePredicate) compareTo(other *PrecedencePredicate) int {
return p.precedence - other.precedence
}
func (p *PrecedencePredicate) equals(other interface{}) bool {
if p == other {
return true
} else if _, ok := other.(*PrecedencePredicate); !ok {
return false
} else {
return p.precedence == other.(*PrecedencePredicate).precedence
}
}
func (p *PrecedencePredicate) hash() int {
return p.precedence * 51
}
func (p *PrecedencePredicate) String() string {
return "{" + strconv.Itoa(p.precedence) + ">=prec}?"
}
func PrecedencePredicatefilterPrecedencePredicates(set *Set) []*PrecedencePredicate {
result := make([]*PrecedencePredicate, 0)
for _, v := range set.values() {
if c2, ok := v.(*PrecedencePredicate); ok {
result = append(result, c2)
}
}
return result
}
// A semantic context which is true whenever none of the contained contexts
// is false.`
type AND struct {
opnds []SemanticContext
}
func NewAND(a, b SemanticContext) *AND {
operands := NewSet(nil, nil)
if aa, ok := a.(*AND); ok {
for _, o := range aa.opnds {
operands.add(o)
}
} else {
operands.add(a)
}
if ba, ok := b.(*AND); ok {
for _, o := range ba.opnds {
operands.add(o)
}
} else {
operands.add(b)
}
precedencePredicates := PrecedencePredicatefilterPrecedencePredicates(operands)
if len(precedencePredicates) > 0 {
// interested in the transition with the lowest precedence
var reduced *PrecedencePredicate
for _, p := range precedencePredicates {
if reduced == nil || p.precedence < reduced.precedence {
reduced = p
}
}
operands.add(reduced)
}
vs := operands.values()
opnds := make([]SemanticContext, len(vs))
for i, v := range vs {
opnds[i] = v.(SemanticContext)
}
and := new(AND)
and.opnds = opnds
return and
}
func (a *AND) equals(other interface{}) bool {
if a == other {
return true
} else if _, ok := other.(*AND); !ok {
return false
} else {
for i, v := range other.(*AND).opnds {
if !a.opnds[i].equals(v) {
return false
}
}
return true
}
}
//
// {@inheritDoc}
//
// <p>
// The evaluation of predicates by a context is short-circuiting, but
// unordered.</p>
//
func (a *AND) evaluate(parser Recognizer, outerContext RuleContext) bool {
for i := 0; i < len(a.opnds); i++ {
if !a.opnds[i].evaluate(parser, outerContext) {
return false
}
}
return true
}
func (a *AND) evalPrecedence(parser Recognizer, outerContext RuleContext) SemanticContext {
differs := false
operands := make([]SemanticContext, 0)
for i := 0; i < len(a.opnds); i++ {
context := a.opnds[i]
evaluated := context.evalPrecedence(parser, outerContext)
differs = differs || (evaluated != context)
if evaluated == nil {
// The AND context is false if any element is false
return nil
} else if evaluated != SemanticContextNone {
// Reduce the result by Skipping true elements
operands = append(operands, evaluated)
}
}
if !differs {
return a
}
if len(operands) == 0 {
// all elements were true, so the AND context is true
return SemanticContextNone
}
var result SemanticContext
for _, o := range operands {
if result == nil {
result = o
} else {
result = SemanticContextandContext(result, o)
}
}
return result
}
func (a *AND) hash() int {
h := murmurInit(37) // Init with a value different from OR
for _, op := range a.opnds {
h = murmurUpdate(h, op.hash())
}
return murmurFinish(h, len(a.opnds))
}
func (a *OR) hash() int {
h := murmurInit(41) // Init with a value different from AND
for _, op := range a.opnds {
h = murmurUpdate(h, op.hash())
}
return murmurFinish(h, len(a.opnds))
}
func (a *AND) String() string {
s := ""
for _, o := range a.opnds {
s += "&& " + fmt.Sprint(o)
}
if len(s) > 3 {
return s[0:3]
}
return s
}
//
// A semantic context which is true whenever at least one of the contained
// contexts is true.
//
type OR struct {
opnds []SemanticContext
}
func NewOR(a, b SemanticContext) *OR {
operands := NewSet(nil, nil)
if aa, ok := a.(*OR); ok {
for _, o := range aa.opnds {
operands.add(o)
}
} else {
operands.add(a)
}
if ba, ok := b.(*OR); ok {
for _, o := range ba.opnds {
operands.add(o)
}
} else {
operands.add(b)
}
precedencePredicates := PrecedencePredicatefilterPrecedencePredicates(operands)
if len(precedencePredicates) > 0 {
// interested in the transition with the lowest precedence
var reduced *PrecedencePredicate
for _, p := range precedencePredicates {
if reduced == nil || p.precedence > reduced.precedence {
reduced = p
}
}
operands.add(reduced)
}
vs := operands.values()
opnds := make([]SemanticContext, len(vs))
for i, v := range vs {
opnds[i] = v.(SemanticContext)
}
o := new(OR)
o.opnds = opnds
return o
}
func (o *OR) equals(other interface{}) bool {
if o == other {
return true
} else if _, ok := other.(*OR); !ok {
return false
} else {
for i, v := range other.(*OR).opnds {
if !o.opnds[i].equals(v) {
return false
}
}
return true
}
}
// <p>
// The evaluation of predicates by o context is short-circuiting, but
// unordered.</p>
//
func (o *OR) evaluate(parser Recognizer, outerContext RuleContext) bool {
for i := 0; i < len(o.opnds); i++ {
if o.opnds[i].evaluate(parser, outerContext) {
return true
}
}
return false
}
func (o *OR) evalPrecedence(parser Recognizer, outerContext RuleContext) SemanticContext {
differs := false
operands := make([]SemanticContext, 0)
for i := 0; i < len(o.opnds); i++ {
context := o.opnds[i]
evaluated := context.evalPrecedence(parser, outerContext)
differs = differs || (evaluated != context)
if evaluated == SemanticContextNone {
// The OR context is true if any element is true
return SemanticContextNone
} else if evaluated != nil {
// Reduce the result by Skipping false elements
operands = append(operands, evaluated)
}
}
if !differs {
return o
}
if len(operands) == 0 {
// all elements were false, so the OR context is false
return nil
}
var result SemanticContext
for _, o := range operands {
if result == nil {
result = o
} else {
result = SemanticContextorContext(result, o)
}
}
return result
}
func (o *OR) String() string {
s := ""
for _, o := range o.opnds {
s += "|| " + fmt.Sprint(o)
}
if len(s) > 3 {
return s[0:3]
}
return s
}
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