package net.sf.saxon.expr;
import net.sf.saxon.Configuration;
import net.sf.saxon.om.Item;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.NumericValue;
import net.sf.saxon.value.SequenceType;
import net.sf.saxon.value.DoubleValue;
/**
* Negate Expression: implements the unary minus operator.
* This expression is initially created as an ArithmeticExpression (or in backwards
* compatibility mode, an ArithmeticExpression10) to take advantage of the type checking code.
* So we don't need to worry about type checking or argument conversion.
*/
public class NegateExpression extends UnaryExpression {
private boolean backwardsCompatible;
/**
* Create a NegateExpression
* @param base the expression that computes the value whose sign is to be reversed
*/
public NegateExpression(Expression base) {
super(base);
}
/**
* Set whether the expression is to be evaluated in XPath 1.0 compatibility mode
* @param compatible true if XPath 1.0 compatibility mode is enabled
*/
public void setBackwardsCompatible(boolean compatible) {
backwardsCompatible = compatible;
}
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
// always called from ArithmeticExpression.typeCheck, so the operand has already been checked.
// Now need to ensure that it's numeric
Expression oldop = operand;
RoleLocator role = new RoleLocator(RoleLocator.UNARY_EXPR, "-", 0);
//role.setSourceLocator(this);
operand = TypeChecker.staticTypeCheck(operand, SequenceType.OPTIONAL_NUMERIC, backwardsCompatible,
role, visitor);
if (operand != oldop) {
adoptChildExpression(operand);
}
return this;
}
/**
* Determine the data type of the expression, if this is known statically
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return operand.getItemType(th);
}
/**
* Evaluate the expression.
*/
public Item evaluateItem(XPathContext context) throws XPathException {
NumericValue v1 = (NumericValue) operand.evaluateItem(context);
if (v1 == null) {
return backwardsCompatible ? DoubleValue.NaN : null;
}
return v1.negate();
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
return new NegateExpression(getBaseExpression().copy());
}
protected String displayOperator(Configuration config) {
return "-";
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (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.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//