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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.elab.ItemEvaluator;
import net.sf.saxon.expr.elab.Elaborator;
import net.sf.saxon.expr.elab.ItemElaborator;
import net.sf.saxon.Configuration;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.om.GroundedValue;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.DoubleValue;
import net.sf.saxon.value.NumericValue;
import net.sf.saxon.value.SequenceType;
import java.util.function.Supplier;
/**
* Negate Expression: implements the unary minus operator.
* This expression is initially created as an ArithmeticExpression (or in backwards
* compatibility mode, an ArithmeticExpression10) to take advantage of the type checking code.
* So we don't need to worry about type checking or argument conversion.
*/
public class NegateExpression extends UnaryExpression {
private boolean backwardsCompatible;
/**
* Create a NegateExpression
*
* @param base the expression that computes the value whose sign is to be reversed
*/
public NegateExpression(Expression base) {
super(base);
}
/**
* Set whether the expression is to be evaluated in XPath 1.0 compatibility mode
*
* @param compatible true if XPath 1.0 compatibility mode is enabled
*/
public void setBackwardsCompatible(boolean compatible) {
backwardsCompatible = compatible;
}
/**
* Ask whether the expression is to be evaluated in XPath 1.0 compatibility mode
*
* @return true if XPath 1.0 compatibility mode is enabled
*/
public boolean isBackwardsCompatible() {
return backwardsCompatible;
}
@Override
protected OperandRole getOperandRole() {
return OperandRole.SINGLE_ATOMIC;
}
/*@NotNull*/
@Override
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
getOperand().typeCheck(visitor, contextInfo);
Supplier role = () -> new RoleDiagnostic(RoleDiagnostic.UNARY_EXPR, "-", 0);
Expression operand = visitor.getConfiguration().getTypeChecker(backwardsCompatible).staticTypeCheck(
getBaseExpression(), SequenceType.OPTIONAL_NUMERIC,
role, visitor);
setBaseExpression(operand);
if (operand instanceof Literal) {
GroundedValue v = ((Literal) operand).getGroundedValue();
if (v instanceof NumericValue) {
return Literal.makeLiteral(((NumericValue) v).negate(), this);
}
}
return this;
}
/**
* Determine the data type of the expression, if this is known statically
*/
/*@NotNull*/
@Override
public ItemType getItemType() {
return getBaseExpression().getItemType().getPrimitiveItemType();
}
@Override
protected int computeCardinality() {
return getBaseExpression().getCardinality() & ~StaticProperty.ALLOWS_MANY;
}
/**
* An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
* This method indicates which of these methods is provided directly. The other methods will always be available
* indirectly, using an implementation that relies on one of the other methods.
*
* @return the implementation method, for example {@link #ITERATE_METHOD} or {@link #EVALUATE_METHOD} or
* {@link #PROCESS_METHOD}
*/
@Override
public int getImplementationMethod() {
return EVALUATE_METHOD;
}
/**
* Evaluate the expression.
*/
@Override
public NumericValue evaluateItem(XPathContext context) throws XPathException {
return (NumericValue)makeElaborator().elaborateForItem().eval(context);
}
/**
* 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) {
NegateExpression exp = new NegateExpression(getBaseExpression().copy(rebindings));
ExpressionTool.copyLocationInfo(this, exp);
return exp;
}
@Override
protected String displayOperator(Configuration config) {
return "-";
}
/**
* 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 "minus";
}
@Override
public void export(ExpressionPresenter out) throws XPathException {
out.startElement("minus", this);
if (backwardsCompatible) {
out.emitAttribute("vn", "1");
}
getBaseExpression().export(out);
out.endElement();
}
/**
* Make an elaborator for this expression
*
* @return a suitable elaborator
*/
@Override
public Elaborator getElaborator() {
return new NegateElaborator();
}
/**
* Elaborator for a negate expression (that is, unary minus)
*/
public static class NegateElaborator extends ItemElaborator {
public ItemEvaluator elaborateForItem() {
final NegateExpression exp = (NegateExpression)getExpression();
final ItemEvaluator argEval = exp.getBaseExpression().makeElaborator().elaborateForItem();
final boolean maybeEmpty = Cardinality.allowsZero(exp.getBaseExpression().getCardinality());
final boolean backwardsCompatible = exp.isBackwardsCompatible();
if (maybeEmpty) {
if (backwardsCompatible) {
return context -> {
NumericValue v1 = (NumericValue) argEval.eval(context);
return v1 == null ? DoubleValue.NaN : v1.negate();
};
} else {
return context -> {
NumericValue v1 = (NumericValue) argEval.eval(context);
return v1 == null ? null : v1.negate();
};
}
} else {
return context -> ((NumericValue) argEval.eval(context)).negate();
}
}
}
}