package net.sf.saxon.expr;
import net.sf.saxon.om.Item;
import net.sf.saxon.sort.AtomicComparer;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.BooleanValue;
import net.sf.saxon.trace.ExpressionPresenter;
/**
* Class to handle comparisons of singletons. Unlike ValueComparison, this class
* converts untyped atomic values to the type of the other argument, and returns false
* (rather than ()) if either operand is ().
*/
public class SingletonComparison extends BinaryExpression implements ComparisonExpression {
private AtomicComparer comparer;
private boolean needsRuntimeCheck = true;
/**
* Create a singleton comparison - that is, a comparison between two singleton (0:1) sequences
* using the general comparison semantics
* @param p1 the first operand
* @param operator the operator
* @param p2 the second operand
* @param checkTypes true if a run-time check for comparability of the operand types is needed
*/
public SingletonComparison(Expression p1, int operator, Expression p2, boolean checkTypes) {
super(p1, operator, p2);
this.needsRuntimeCheck = checkTypes;
}
public void setAtomicComparer(AtomicComparer comp) {
comparer = comp;
}
public AtomicComparer getAtomicComparer() {
return comparer;
}
public int getSingletonOperator() {
return operator;
}
/**
* Determine whether untyped atomic values should be converted to the type of the other operand
* @return true if untyped values should be converted to the type of the other operand, false if they
* should be converted to strings.
*/
public boolean convertsUntypedToOther() {
return true;
}
/**
* Determine the static cardinality. Returns [1..1]
*/
public int computeCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Determine the data type of the expression
* @return Type.BOOLEAN
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return BuiltInAtomicType.BOOLEAN;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
SingletonComparison sc = new SingletonComparison(operand0.copy(), operator, operand1.copy(), needsRuntimeCheck);
sc.comparer = comparer;
return sc;
}
/**
* Determine whether a run-time check is needed to check that the types of the arguments
* are comparable
* @return true if a run-time check is needed
*/
public boolean needsRuntimeComparabilityCheck() {
return needsRuntimeCheck;
}
/**
* Evaluate the expression in a given context
* @param context the given context for evaluation
* @return a BooleanValue representing the result of the numeric comparison of the two operands
*/
public Item evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
/**
* Evaluate the expression in a boolean context
* @param context the given context for evaluation
* @return a boolean representing the result of the numeric comparison of the two operands
*/
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
AtomicValue v1 = (AtomicValue)operand0.evaluateItem(context);
if (v1==null) {
return false;
}
AtomicValue v2 = (AtomicValue)operand1.evaluateItem(context);
if (v2==null) {
return false;
}
try {
return GeneralComparison.compare(v1, operator, v2, comparer, needsRuntimeCheck, context);
} catch (XPathException e) {
// re-throw the exception with location information added
e.maybeSetLocation(this);
e.maybeSetContext(context);
throw e;
}
}
protected void explainExtraAttributes(ExpressionPresenter out) {
out.emitAttribute("cardinality", "singleton");
}
}
//
// 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.
//