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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// 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/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package net.sf.saxon.functions;

import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.parser.ExpressionTool;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.Optimizer;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;

/**
* XPath 2.0 unordered() function
*/

public class Unordered extends CompileTimeFunction {

    /*@NotNull*/
    public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
        Expression exp = super.typeCheck(visitor, contextItemType);
        if (exp instanceof Unordered) {
            Optimizer opt = visitor.getConfiguration().obtainOptimizer();
            return ExpressionTool.unsorted(opt, ((Unordered)exp).argument[0], true);
        }
        return exp;
    }

    /*@NotNull*/
    public Expression optimize(/*@NotNull*/ ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
        Expression exp = super.optimize(visitor, contextItemType);
        if (exp instanceof Unordered) {
            return ExpressionTool.unsorted(visitor.getConfiguration().obtainOptimizer(),
                    ((Unordered) exp).argument[0], true);
        }
        return exp;
    }

    /**
     * Replace this expression by an expression that returns the same result but without
     * regard to order
     *
     * @param retainAllNodes true if all nodes in the result must be retained; false
     *                       if duplicates can be eliminated
     */
    @Override
    public Expression unordered(boolean retainAllNodes) throws XPathException {
        return argument[0].unordered(retainAllNodes);
    }

    /**
    * preEvaluate: called if the argument is constant
     * @param visitor an expression visitor
     */

    public Expression preEvaluate(ExpressionVisitor visitor) throws XPathException {
        return argument[0];
    }

    /**
     * Evaluate the expression
     *
     * @param context   the dynamic evaluation context
     * @param arguments the values of the arguments, supplied as Sequences
     * @return the result of the evaluation, in the form of a Sequence
     * @throws net.sf.saxon.trans.XPathException
     *          if a dynamic error occurs during the evaluation of the expression
     */
    public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
        return arguments[0];
    }
}