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// Copyright 2017 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.syntax;
import com.google.devtools.build.lib.events.Location;
import java.io.IOException;
/** Syntax node for a unary operator expression. */
public final class UnaryOperatorExpression extends Expression {
private final UnaryOperator operator;
private final Expression operand;
public UnaryOperatorExpression(UnaryOperator operator, Expression operand) {
this.operator = operator;
this.operand = operand;
}
public UnaryOperator getOperator() {
return operator;
}
public Expression getOperand() {
return operand;
}
@Override
public void prettyPrint(Appendable buffer) throws IOException {
// TODO(bazel-team): Possibly omit parentheses when they are not needed according to operator
// precedence rules. This requires passing down more contextual information.
buffer.append(operator.toString());
buffer.append('(');
operand.prettyPrint(buffer);
buffer.append(')');
}
@Override
public String toString() {
// All current and planned unary operators happen to be prefix operators.
// Non-symbolic operators have trailing whitespace built into their name.
//
// Note that this omits the parentheses for brevity, but is not correct in general due to
// operator precedence rules. For example, "(not False) in mylist" prints as
// "not False in mylist", which evaluates to opposite results in the case that mylist is empty.
return operator.toString() + operand;
}
private static Object evaluate(
UnaryOperator operator,
Object value,
Location loc)
throws EvalException, InterruptedException {
switch (operator) {
case NOT:
return !EvalUtils.toBoolean(value);
case MINUS:
if (!(value instanceof Integer)) {
throw new EvalException(
loc,
String.format(
"unsupported operand type for -: '%s'", EvalUtils.getDataTypeName(value)));
}
try {
return Math.negateExact((Integer) value);
} catch (ArithmeticException e) {
// Fails for -MIN_INT.
throw new EvalException(loc, e.getMessage());
}
default:
throw new AssertionError("Unsupported unary operator: " + operator);
}
}
@Override
Object doEval(Environment env) throws EvalException, InterruptedException {
return evaluate(operator, operand.eval(env), getLocation());
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
public Kind kind() {
return Kind.UNARY_OPERATOR;
}
}
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