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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically embedded into Java applications to provide scripting to end users.
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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.javascript.ast;

import org.mozilla.javascript.Token;

/**
 * AST node representing unary operators such as {@code typeof} and {@code delete}. The type field
 * is set to the appropriate Token type for the operator. The node length spans from the operator to
 * the end of the operand.
 *
 * The {@code default xml namespace = <expr>} statement in E4X (JavaScript 1.6) is
 * represented as a {@code UnaryExpression} of node type {@link Token#DEFAULTNAMESPACE}, wrapped
 * with an {@link ExpressionStatement}.
 */
public class UnaryExpression extends AstNode {

    private AstNode operand;

    public UnaryExpression() {}

    public UnaryExpression(int pos) {
        super(pos);
    }

    /** Constructs a new UnaryExpression */
    public UnaryExpression(int pos, int len) {
        super(pos, len);
    }

    /**
     * Constructs a new UnaryExpression with the specified operator and operand. It sets the parent
     * of the operand, and sets its own bounds to encompass the operator and operand.
     *
     * @param operator the node type
     * @param operatorPosition the absolute position of the operator.
     * @param operand the operand expression
     * @throws IllegalArgumentException} if {@code operand} is {@code null}
     */
    public UnaryExpression(int operator, int operatorPosition, AstNode operand) {
        assertNotNull(operand);
        int beg = operand.getPosition();
        // JavaScript only has ++ and -- postfix operators, so length is 2
        int end = operand.getPosition() + operand.getLength();
        setBounds(beg, end);
        setOperator(operator);
        setOperand(operand);
    }

    /** Returns operator token – alias for {@link #getType} */
    public int getOperator() {
        return type;
    }

    /**
     * Sets operator – same as {@link #setType}, but throws an exception if the operator is
     * invalid
     *
     * @throws IllegalArgumentException if operator is not a valid Token code
     */
    public void setOperator(int operator) {
        if (!Token.isValidToken(operator))
            throw new IllegalArgumentException("Invalid token: " + operator);
        setType(operator);
    }

    public AstNode getOperand() {
        return operand;
    }

    /**
     * Sets the operand, and sets its parent to be this node.
     *
     * @throws IllegalArgumentException} if {@code operand} is {@code null}
     */
    public void setOperand(AstNode operand) {
        assertNotNull(operand);
        this.operand = operand;
        operand.setParent(this);
    }

    @Override
    public String toSource(int depth) {
        StringBuilder sb = new StringBuilder();
        sb.append(makeIndent(depth));
        int type = getType();
        sb.append(operatorToString(type));
        if (type == Token.TYPEOF || type == Token.DELPROP || type == Token.VOID) {
            sb.append(" ");
        }
        sb.append(operand.toSource());

        return sb.toString();
    }

    /** Visits this node, then the operand. */
    @Override
    public void visit(NodeVisitor v) {
        if (v.visit(this)) {
            operand.visit(v);
        }
    }
}