package client.net.sf.saxon.ce.expr;
import client.net.sf.saxon.ce.om.Item;
import client.net.sf.saxon.ce.trans.XPathException;
import client.net.sf.saxon.ce.type.ItemType;
import client.net.sf.saxon.ce.type.TypeHierarchy;
import client.net.sf.saxon.ce.value.NumericValue;
import client.net.sf.saxon.ce.value.SequenceType;
import client.net.sf.saxon.ce.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 {
Expression oldop = operand;
RoleLocator role = new RoleLocator(RoleLocator.UNARY_EXPR, "-", 0);
operand = TypeChecker.staticTypeCheck(operand, SequenceType.OPTIONAL_NUMERIC, backwardsCompatible,
role, visitor);
operand = visitor.typeCheck(operand, contextItemType);
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();
}
}
// 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.