package net.sf.saxon.functions;
import net.sf.saxon.expr.*;
import net.sf.saxon.om.Item;
import net.sf.saxon.pattern.NodeTest;
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.BooleanValue;
import net.sf.saxon.Configuration;
/**
* This class supports the XPath functions boolean(), not(), true(), and false()
*/
public class BooleanFn extends SystemFunction implements Negatable {
public static final int BOOLEAN = 0;
public static final int NOT = 1;
public static final int TRUE = 2;
public static final int FALSE = 3;
//private boolean argIsSingleton = false;
/**
* Simplify the function call. Default method is to simplify each of the supplied arguments and
* evaluate the function if all are now known.
* @param visitor an expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
switch (operation) {
case BOOLEAN:
case NOT:
return super.simplify(visitor);
case TRUE:
return Literal.makeLiteral(BooleanValue.TRUE);
case FALSE:
return Literal.makeLiteral(BooleanValue.FALSE);
default:
throw new UnsupportedOperationException("Unknown boolean operation");
}
}
/**
* Static analysis: prevent sorting of the argument
*/
public void checkArguments(ExpressionVisitor visitor) throws XPathException {
super.checkArguments(visitor);
if (operation==BOOLEAN || operation==NOT) {
XPathException err = TypeChecker.ebvError(argument[0], visitor.getConfiguration().getTypeHierarchy());
if (err != null) {
err.setLocator(this);
throw err;
}
Optimizer opt = visitor.getConfiguration().getOptimizer();
argument[0] = ExpressionTool.unsortedIfHomogeneous(opt, argument[0]);
}
}
/**
* 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 net.sf.saxon.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 if (operation == NOT) {
Expression ebv = rewriteEffectiveBooleanValue(argument[0], visitor, contextItemType);
if (ebv != null) {
argument[0] = ebv;
}
if (argument[0] instanceof Negatable && ((Negatable)argument[0]).isNegatable(visitor)) {
return ((Negatable)argument[0]).negate().optimize(visitor, contextItemType);
}
return this;
}
}
return e;
}
/**
* Check whether this specific instance of the expression is negatable
*
* @return true if it is
*/
public boolean isNegatable(ExpressionVisitor visitor) {
return true;
}
/**
* Create an expression that returns the negation of this expression
* @return the negated expression
*/
public Expression negate() {
switch (operation) {
case BOOLEAN:
return SystemFunction.makeSystemFunction("not", getArguments());
case NOT:
return SystemFunction.makeSystemFunction("boolean", getArguments());
case TRUE:
return new Literal(BooleanValue.FALSE);
case FALSE:
return new Literal(BooleanValue.TRUE);
default:
throw new AssertionError("Unknown operation");
}
}
/**
* 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();
exp = ExpressionTool.unsortedIfHomogeneous(config.getOptimizer(), exp);
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.getItemType(th) instanceof NodeTest) {
// rewrite boolean(x) => exists(x)
FunctionCall exists = SystemFunction.makeSystemFunction("exists", new Expression[]{exp});
exists.setLocationId(exp.getLocationId());
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 {
try {
switch (operation) {
case BOOLEAN:
return argument[0].effectiveBooleanValue(c);
case NOT:
return !argument[0].effectiveBooleanValue(c);
case TRUE:
return true;
case FALSE:
return false;
default:
throw new UnsupportedOperationException("Unknown boolean operation");
}
} catch (XPathException e) {
e.maybeSetLocation(this);
e.maybeSetContext(c);
throw e;
}
}
}
//
// 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.
//