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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// 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.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.functions.BooleanFn;
import net.sf.saxon.functions.SystemFunctionCall;
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 java.util.Iterator;
import java.util.List;
/**
* Boolean expression: two truth values combined using AND or OR.
*/
public abstract class BooleanExpression extends BinaryExpression implements Negatable {
/**
* Construct a boolean expression
* @param p1 the first operand
* @param operator one of {@link Token#AND} or {@link Token#OR}
* @param p2 the second operand
*/
public BooleanExpression(Expression p1, int operator, Expression p2) {
super(p1, operator, p2);
}
/**
* Get a name identifying the kind of expression, in terms meaningful to a user.
*
* @return a name identifying the kind of expression, in terms meaningful to a user.
* The name will always be in the form of a lexical XML QName, and should match the name used
* in explain() output displaying the expression.
*/
@Override
public String getExpressionName() {
return Token.tokens[getOperator()] + "-expression";
}
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
Expression e = super.typeCheck(visitor, contextItemType);
if (e == this) {
XPathException err0 = TypeChecker.ebvError(operand0, visitor.getConfiguration().getTypeHierarchy());
if (err0 != null) {
err0.setLocator(this);
throw err0;
}
XPathException err1 = TypeChecker.ebvError(operand1, visitor.getConfiguration().getTypeHierarchy());
if (err1 != null) {
err1.setLocator(this);
throw err1;
}
// Precompute the EBV of any constant operand
if (operand0 instanceof Literal && !(((Literal)operand0).getValue() instanceof BooleanValue)) {
operand0 = Literal.makeLiteral(BooleanValue.get(operand0.effectiveBooleanValue(null)));
}
if (operand1 instanceof Literal && !(((Literal)operand1).getValue() instanceof BooleanValue)) {
operand1 = Literal.makeLiteral(BooleanValue.get(operand1.effectiveBooleanValue(null)));
}
}
return e;
}
/**
* Determine the static cardinality. Returns [1..1]
*/
public int computeCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Perform optimisation of an expression and its subexpressions.
*
* 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.
*
* @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)
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
final Expression e = super.optimize(visitor, contextItemType);
if (e != this) {
return e;
}
Optimizer opt = visitor.getConfiguration().obtainOptimizer();
operand0 = ExpressionTool.unsortedIfHomogeneous(opt, operand0);
operand1 = ExpressionTool.unsortedIfHomogeneous(opt, operand1);
Expression op0 = BooleanFn.rewriteEffectiveBooleanValue(operand0, visitor, contextItemType);
if (op0 != null) {
operand0 = op0;
}
Expression op1 = BooleanFn.rewriteEffectiveBooleanValue(operand1, visitor, contextItemType);
if (op1 != null) {
operand1 = op1;
}
return this;
}
protected Expression forceToBoolean(Expression in, TypeHierarchy th) {
if (in.getItemType(th) == BuiltInAtomicType.BOOLEAN && in.getCardinality() == StaticProperty.ALLOWS_ONE) {
return in;
} else {
return SystemFunctionCall.makeSystemFunction("boolean", new Expression[]{in});
}
}
/**
* Check whether this specific instance of the expression is negatable
*
* @return true if it is
*/
public boolean isNegatable(ExpressionVisitor visitor) {
return true;
}
/**
* Return the negation of this boolean expression, that is, an expression that returns true
* when this expression returns false, and vice versa
*
* @return the negation of this expression
*/
public abstract Expression negate();
/**
* Evaluate the expression
*/
public BooleanValue evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
/**
* Evaluate as a boolean.
*/
public abstract boolean effectiveBooleanValue(XPathContext c) throws XPathException;
/**
* Determine the data type of the expression
* @return BuiltInAtomicType.BOOLEAN
* @param th the type hierarchy cache
*/
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
return BuiltInAtomicType.BOOLEAN;
}
/**
* Construct a list containing the "anded" subexpressions of an expression:
* if the expression is (A and B and C), this returns (A, B, C).
* @param exp the expression to be decomposed
* @param list the list to which the subexpressions are to be added.
*/
public static void listAndComponents(Expression exp, List list) {
if (exp instanceof BooleanExpression && ((BooleanExpression)exp).getOperator() == Token.AND) {
for (Iterator iter = exp.iterateSubExpressions(); iter.hasNext();) {
listAndComponents((Expression)iter.next(), list);
}
} else {
list.add(exp);
}
}
}