net.sf.saxon.expr
Class NegateExpression

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.UnaryExpression
          net.sf.saxon.expr.NegateExpression

All Implemented Interfaces:

Serializable, SourceLocator, EvaluableItem, SequenceIterable, InstructionInfoProvider

public class NegateExpression
extends UnaryExpression

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.

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

NegateExpression(Expression base)
Create a NegateExpression

Method Summary

Expression	copy() Copy an expression.
Item	evaluateItem(XPathContext context) Evaluate the expression.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the expression, if this is known statically
void	setBackwardsCompatible(boolean compatible) Set whether the expression is to be evaluated in XPath 1.0 compatibility mode
Expression	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Type-check the expression.

Methods inherited from class net.sf.saxon.expr.UnaryExpression

computeCardinality, computeSpecialProperties, equals, explain, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, effectiveBooleanValue, evaluateAsString, explain, findParentOf, getCardinality, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, markTailFunctionCalls, process, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

NegateExpression

public NegateExpression(Expression base)

Create a NegateExpression

Parameters:

base - the expression that computes the value whose sign is to be reversed

Method Detail

setBackwardsCompatible

public void setBackwardsCompatible(boolean compatible)

Set whether the expression is to be evaluated in XPath 1.0 compatibility mode

Parameters:

compatible - true if XPath 1.0 compatibility mode is enabled

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException

Description copied from class: UnaryExpression

Type-check the expression. Default implementation for unary operators that accept any kind of operand

Overrides:

typeCheck in class UnaryExpression

Parameters:

visitor - an expression visitor

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 Type.ITEM_TYPE

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the expression, if this is known statically

Overrides:

getItemType in class UnaryExpression

Parameters:

th - the type hierarchy cache

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression.

Specified by:

evaluateItem in interface EvaluableItem

Overrides:

evaluateItem in class Expression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression