net.sf.saxon.xpath

Class XPathFunctionCall

public class XPathFunctionCall extends FunctionCall

This class is an expression that calls an external function supplied using the JAXP XPathFunction interface
Constructor Summary
XPathFunctionCall(XPathFunction function)
Default constructor
Method Summary
PathMap.PathMapNodeSetaddToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap.
protected SequenceIteratorcall(ValueRepresentation[] argValues, XPathContext context)
Call an extension function previously identified using the bind() method.
voidcheckArguments(ExpressionVisitor visitor)
Method called by the expression parser when all arguments have been supplied
intcomputeCardinality()
Determine the cardinality of the result
Expressioncopy()
Copy an expression.
intgetIntrinsicDependencies()
Determine which aspects of the context the expression depends on.
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression, if possible.
SequenceIteratoriterate(XPathContext context)
Evaluate the function.
ExpressionpreEvaluate(ExpressionVisitor visitor)
preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the external function might have side-effects and might use the context)

Constructor Detail

XPathFunctionCall

public XPathFunctionCall(XPathFunction function)
Default constructor

Method Detail

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Parameters: pathMap the PathMap to which the expression should be added pathMapNodeSet

Returns: the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

call

protected SequenceIterator call(ValueRepresentation[] argValues, XPathContext context)
Call an extension function previously identified using the bind() method. A subclass can override this method.

Parameters: argValues The values of the arguments context The XPath dynamic context

Returns: The value returned by the extension function

checkArguments

public void checkArguments(ExpressionVisitor visitor)
Method called by the expression parser when all arguments have been supplied

computeCardinality

public int computeCardinality()
Determine the cardinality of the result

Returns: ZERO_OR_MORE (we don't know)

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

getIntrinsicDependencies

public int getIntrinsicDependencies()
Determine which aspects of the context the expression depends on. XPath external functions are given no access to context information so they cannot have any dependencies on it.

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible. All expressions return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method will always return a result, though it may be the best approximation that is available at the time.

Parameters: th the type hierarchy cache

Returns: the item type

iterate

public SequenceIterator iterate(XPathContext context)
Evaluate the function.

Parameters: context The context in which the function is to be evaluated

Returns: a Value representing the result of the function.

Throws: XPathException if the function cannot be evaluated.

preEvaluate

public Expression preEvaluate(ExpressionVisitor visitor)
preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the external function might have side-effects and might use the context)

Parameters: visitor an expression visitor