net.sf.saxon.expr
Class NegateExpression

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.UnaryExpression
          extended by 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


Copyright (C) Michael H. Kay. All rights reserved.