net.sf.saxon.expr
Class NumericPromoter

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.UnaryExpression
          extended by net.sf.saxon.expr.NumericPromoter
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator
Direct Known Subclasses:
PromoteToDouble, PromoteToFloat

public abstract class NumericPromoter
extends UnaryExpression

A NumericPromoter performs numeric promotion on each item in a supplied sequence. There are two subclasses, to handle promotion to double and promotion to float

See Also:
Serialized Form

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, locationId, PROCESS_METHOD, staticProperties
 
Constructor Summary
NumericPromoter(Expression exp)
           
 
Method Summary
 Item evaluateItem(XPathContext context)
          Evaluate as an Item.
 void explain(ExpressionPresenter out)
          Diagnostic print of expression structure.
 SequenceIterator iterate(XPathContext context)
          Iterate over the sequence of values
 Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
          Optimize the expression
protected abstract  AtomicValue promote(AtomicValue value, XPathContext context)
          Perform the promotion
 Expression simplify(ExpressionVisitor visitor)
          Simplify an expression
 Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
          Type-check the expression
 
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeCardinality, computeSpecialProperties, displayExpressionName, displayOperator, equals, getBaseExpression, getItemType, hashCode, iterateSubExpressions, promote, replaceSubExpression, toString
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, copy, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

NumericPromoter

public NumericPromoter(Expression exp)
Method Detail

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
Simplify an expression

Overrides:
simplify in class UnaryExpression
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
Type-check the expression

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)

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
                    throws XPathException
Optimize the expression

Overrides:
optimize 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 if appropriate to optimize execution
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Iterate over the sequence of values

Specified by:
iterate in interface SequenceIterable
Overrides:
iterate in class Expression
Parameters:
context - supplies the context for evaluation
Returns:
a SequenceIterator that can be used to iterate over the result of the expression
Throws:
XPathException - if any dynamic error occurs evaluating the expression

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate as an Item. This should only be called if the expression has cardinality zero-or-one

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

promote

protected abstract AtomicValue promote(AtomicValue value,
                                       XPathContext context)
                                throws XPathException
Perform the promotion

Parameters:
value - the numeric or untyped atomic value to be promoted
context - the XPath dynamic evaluation context
Returns:
the value that results from the promotion
Throws:
XPathException

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Overrides:
explain in class UnaryExpression
Parameters:
out - the expression presenter used to display the structure


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