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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.query2.engine;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
/**
* A binary algebraic set operation.
*
* <pre>
* expr ::= expr (INTERSECT expr)+
* | expr ('^' expr)+
* | expr (UNION expr)+
* | expr ('+' expr)+
* | expr (EXCEPT expr)+
* | expr ('-' expr)+
* </pre>
*/
class BinaryOperatorExpression extends QueryExpression {
private final Lexer.TokenKind operator; // ::= INTERSECT/CARET | UNION/PLUS | EXCEPT/MINUS
private final ImmutableList<QueryExpression> operands;
BinaryOperatorExpression(Lexer.TokenKind operator,
List<QueryExpression> operands) {
Preconditions.checkState(operands.size() > 1);
this.operator = operator;
this.operands = ImmutableList.copyOf(operands);
}
@Override
public <T> Set<T> eval(QueryEnvironment<T> env) throws QueryException, InterruptedException {
Set<T> lhsValue = new LinkedHashSet<>(operands.get(0).eval(env));
for (int i = 1; i < operands.size(); i++) {
Set<T> rhsValue = operands.get(i).eval(env);
switch (operator) {
case INTERSECT:
case CARET:
lhsValue.retainAll(rhsValue);
break;
case UNION:
case PLUS:
lhsValue.addAll(rhsValue);
break;
case EXCEPT:
case MINUS:
lhsValue.removeAll(rhsValue);
break;
default:
throw new IllegalStateException("operator=" + operator);
}
}
return lhsValue;
}
@Override
public void collectTargetPatterns(Collection<String> literals) {
for (QueryExpression subExpression : operands) {
subExpression.collectTargetPatterns(literals);
}
}
@Override
public String toString() {
StringBuilder result = new StringBuilder();
for (int i = 1; i < operands.size(); i++) {
result.append("(");
}
result.append(operands.get(0));
for (int i = 1; i < operands.size(); i++) {
result.append(" " + operator.getPrettyName() + " " + operands.get(i) + ")");
}
return result.toString();
}
}
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