package client.net.sf.saxon.ce.functions;
import client.net.sf.saxon.ce.Configuration;
import client.net.sf.saxon.ce.expr.*;
import client.net.sf.saxon.ce.om.Item;
import client.net.sf.saxon.ce.pattern.NodeTest;
import client.net.sf.saxon.ce.trans.XPathException;
import client.net.sf.saxon.ce.type.BuiltInAtomicType;
import client.net.sf.saxon.ce.type.ItemType;
import client.net.sf.saxon.ce.type.TypeHierarchy;
import client.net.sf.saxon.ce.value.BooleanValue;
/**
* This class supports the XPath functions boolean(), not(), true(), and false()
*/
public class BooleanFn extends SystemFunction {
public BooleanFn(int operation) {
this.operation = operation;
}
public BooleanFn newInstance() {
return new BooleanFn(operation);
}
public static final int BOOLEAN = 0;
public static final int NOT = 1;
/**
* Static analysis: prevent sorting of the argument
*/
public void checkArguments(ExpressionVisitor visitor) throws XPathException {
super.checkArguments(visitor);
XPathException err = TypeChecker.ebvError(argument[0], visitor.getConfiguration().getTypeHierarchy());
if (err != null) {
err.setLocator(getSourceLocator());
throw err;
}
}
/**
* Perform optimisation of an expression and its subexpressions.
* <p/>
* <p>This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.</p>
*
* @param visitor an expression visitor
* @param contextItemType the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link client.net.sf.saxon.ce.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
Expression e = super.optimize(visitor, contextItemType);
if (e == this) {
// if (argument[0].getCardinality() == StaticProperty.EXACTLY_ONE) {
// argIsSingleton = true;
// }
if (operation == BOOLEAN) {
Expression ebv = rewriteEffectiveBooleanValue(argument[0], visitor, contextItemType);
return (ebv == null ? this : ebv.optimize(visitor, contextItemType));
} else {
Expression ebv = rewriteEffectiveBooleanValue(argument[0], visitor, contextItemType);
if (ebv != null) {
argument[0] = ebv;
}
return this;
}
}
return e;
}
/**
* Optimize an expression whose effective boolean value is required
* @param exp the expression whose EBV is to be evaluated
* @param visitor an expression visitor
* @param contextItemType the type of the context item for this expression
* @return an expression that returns the EBV of exp, or null if no optimization was possible
* @throws XPathException if static errors are found
*/
public static Expression rewriteEffectiveBooleanValue(
Expression exp, ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
Configuration config = visitor.getConfiguration();
TypeHierarchy th = config.getTypeHierarchy();
if (exp instanceof ValueComparison) {
ValueComparison vc = (ValueComparison)exp;
if (vc.getResultWhenEmpty() == null) {
vc.setResultWhenEmpty(BooleanValue.FALSE);
}
return exp;
} else if (exp instanceof BooleanFn && ((BooleanFn)exp).operation == BooleanFn.BOOLEAN) {
return ((BooleanFn)exp).getArguments()[0];
} else if (th.isSubType(exp.getItemType(th), BuiltInAtomicType.BOOLEAN) &&
exp.getCardinality() == StaticProperty.EXACTLY_ONE) {
return exp;
} else if (exp instanceof Count) {
// rewrite boolean(count(x)) => exists(x)
FunctionCall exists = SystemFunction.makeSystemFunction("exists", ((Count)exp).getArguments());
exists.setSourceLocator(exp.getSourceLocator());
return exists.optimize(visitor, contextItemType);
} else if (exp.getItemType(th) instanceof NodeTest) {
// rewrite boolean(x) => exists(x)
FunctionCall exists = SystemFunction.makeSystemFunction("exists", new Expression[]{exp});
exists.setSourceLocator(exp.getSourceLocator());
return exists.optimize(visitor, contextItemType);
} else {
return null;
}
}
/**
* Evaluate the function
*/
public Item evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
/**
* Evaluate the effective boolean value
*/
public boolean effectiveBooleanValue(XPathContext c) throws XPathException {
boolean b = argument[0].effectiveBooleanValue(c);
return (operation == BOOLEAN ? b : !b);
}
}
// 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.