net.sf.saxon.expr

Class NegateExpression

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator

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.

Field Summary

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

operand

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

NegateExpression(Expression base)
Create a NegateExpression

Method Summary

Expression
copy()
Copy an expression.
protected String
displayOperator(Configuration config)
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)
Perform type checking of an expression and its subexpressions.

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

computeCardinality, computeSpecialProperties, displayExpressionName, displayOperator, equals, explain, getBaseExpression, getItemType, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

NegateExpression

public NegateExpression(Expression base)
Create a NegateExpression
Parameters:
base - the expression that computes the value whose sign is to be reversed

Method Details

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

displayOperator

protected String displayOperator(Configuration config)
Overrides:
displayOperator in interface UnaryExpression

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate the expression.
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface Expression

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression, if this is known statically
Overrides:
getItemType in interface UnaryExpression
Parameters:
th - the type hierarchy cache

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
Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:
typeCheck in interface 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)