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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 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.SystemFunction;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.BooleanValue;
public class OrExpression extends BooleanExpression {
/**
* Construct a boolean OR expression
*
* @param p1 the first operand
* @param p2 the second operand
*/
public OrExpression(Expression p1, Expression p2) {
super(p1, Token.OR, p2);
}
@Override
protected Expression preEvaluate() {
if (Literal.hasEffectiveBooleanValue(getLhsExpression(), true) || Literal.hasEffectiveBooleanValue(getRhsExpression(), true)) {
// A or true() => true()
// true() or B => true()
return Literal.makeLiteral(BooleanValue.TRUE, this);
} else if (Literal.hasEffectiveBooleanValue(getLhsExpression(), false)) {
// false() or B => B
return forceToBoolean(getRhsExpression());
} else if (Literal.hasEffectiveBooleanValue(getRhsExpression(), false)) {
// A or false() => A
return forceToBoolean(getLhsExpression());
} else {
return this;
}
}
/**
* 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*/
@Override
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
final Expression e = super.optimize(visitor, contextItemType);
if (e != this) {
return e;
}
// If this is a top-level or-expression then try to replace multiple branches with a general comparison
if (!(getParentExpression() instanceof OrExpression)) {
final Expression e2 = visitor.obtainOptimizer().tryGeneralComparison(visitor, contextItemType, this);
if (e2 != null && e2 != this) {
return e2;
}
}
return this;
}
@Override
public double getCost() {
// Assume the RHS will be evaluated 50% of the time
return getLhsExpression().getCost() + getRhsExpression().getCost() / 2;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
* @param rebindings variables that need to be re-bound
*/
/*@NotNull*/
@Override
public Expression copy(RebindingMap rebindings) {
OrExpression exp = new OrExpression(getLhsExpression().copy(rebindings), getRhsExpression().copy(rebindings));
ExpressionTool.copyLocationInfo(this, exp);
return exp;
}
/**
* 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
*/
@Override
public Expression negate() {
// Apply de Morgan's laws
// not(A or B) => not(A) and not(B)
Expression not0 = SystemFunction.makeCall("not", getRetainedStaticContext(), getLhsExpression());
Expression not1 = SystemFunction.makeCall("not", getRetainedStaticContext(), getRhsExpression());
AndExpression result = new AndExpression(not0, not1);
ExpressionTool.copyLocationInfo(this, result);
return result;
}
/**
* Get the element name used to identify this expression in exported expression format
*
* @return the element name used to identify this expression
*/
@Override
protected String tag() {
return "or";
}
/**
* Evaluate as a boolean.
*/
@Override
public boolean effectiveBooleanValue(XPathContext c) throws XPathException {
return getLhsExpression().effectiveBooleanValue(c) || getRhsExpression().effectiveBooleanValue(c);
}
}