////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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.expr;

import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;

/**
 * A generic interface for calling expressions by supplying the values of their subexpressions
 */

public interface Callable {

    /**
     * Call the Callable.
     * @param context the dynamic evaluation context
     * @param arguments the values of the arguments, supplied as Sequences.
     * <p>Generally it is advisable, if calling iterate() to process a supplied sequence, to
     * call it only once; if the value is required more than once, it should first be converted
     * to a {@link net.sf.saxon.om.GroundedValue} by calling the utility methd
     * SequenceTool.toGroundedValue().</p>
     * <p>If the expected value is a single item, the item should be obtained by calling
     * Sequence.head(): it cannot be assumed that the item will be passed as an instance of
     * {@link net.sf.saxon.om.Item} or {@link net.sf.saxon.value.AtomicValue}.</p>
     * <p>It is the caller's responsibility to perform any type conversions required
     * to convert arguments to the type expected by the callee. An exception is where
     * this Callable is explicitly an argument-converting wrapper around the original
     * Callable.</p>
     * @return the result of the evaluation, in the form of a Sequence. It is the responsibility
     * of the callee to ensure that the type of result conforms to the expected result type.
     * @throws XPathException if a dynamic error occurs during the evaluation of the expression
     */
	
	/*@Nullable*/
    public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException;

}
