com.saxonica.hof
Class FunctionSequenceCoercer

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.UnaryExpression
          extended by com.saxonica.hof.FunctionSequenceCoercer
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

public final class FunctionSequenceCoercer
extends UnaryExpression

An FunctionSequenceCoercer performs function coercion on a sequence of function items

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
FunctionSequenceCoercer(Expression sequence, FunctionType requiredItemType, RoleLocator role, ExpressionVisitor visitor)
          Constructor
 
Method Summary
 int computeCardinality()
          Determine the static cardinality of the expression
 int computeSpecialProperties()
          Determine the special properties of this expression
 Expression copy()
          Copy an expression.
 boolean equals(Object other)
          Is this expression the same as another expression?
 Item evaluateItem(XPathContext context)
          Evaluate as an Item.
 void explain(ExpressionPresenter destination)
          Diagnostic print of expression structure.
 ItemType getItemType(TypeHierarchy th)
          Determine the data type of the items returned by the expression, if possible
 SequenceIterator iterate(XPathContext context)
          Iterate over the sequence of values
 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
displayExpressionName, displayOperator, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, toString
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, 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

FunctionSequenceCoercer

public FunctionSequenceCoercer(Expression sequence,
                               FunctionType requiredItemType,
                               RoleLocator role,
                               ExpressionVisitor visitor)
Constructor

Parameters:
sequence - this must be a sequence of function item values. This is not checked; a ClassCastException will occur if the precondition is not satisfied.
requiredItemType - the function item type to which all items in the sequence should be converted, using the rules for function coercion.
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)

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression

Overrides:
computeSpecialProperties in class UnaryExpression
Returns:
StaticProperty.NON_CREATIVE.

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

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 FunctionSequenceCoercer 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

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible

Overrides:
getItemType in class UnaryExpression
Parameters:
th - the type hierarchy cache
Returns:
a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)

computeCardinality

public int computeCardinality()
Determine the static cardinality of the expression

Overrides:
computeCardinality in class UnaryExpression
Returns:
the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

equals

public boolean equals(Object other)
Is this expression the same as another expression?

Overrides:
equals in class UnaryExpression

explain

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

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


Copyright (c) Saxonica Limited. All rights reserved.