com.icl.saxon.expr

Class FilterExpression


(package private) class FilterExpression
extends NodeSetExpression

A FilterExpression contains a base expression and a filter predicate, which may be an integer expression (positional filter), or a boolean expression (qualifier)

Field Summary

Fields inherited from class com.icl.saxon.expr.Expression

staticContext

Constructor Summary

FilterExpression(Expression start, Expression filter)
Constructor

Method Summary

void
display(int level)
Diagnostic print of expression structure
NodeEnumeration
enumerate(Context context, boolean sort)
Evaluate the filter expression in a given context to return a Node Enumeration
int
getDependencies()
Determine which aspects of the context the expression depends on.
boolean
isContextDocumentNodeSet()
Determine, in the case of an expression whose data type is Value.NODESET, whether all the nodes in the node-set are guaranteed to come from the same document as the context node.
Expression
reduce(int dep, Context context)
Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
Expression
simplify()
Simplify an expression

Methods inherited from class com.icl.saxon.expr.NodeSetExpression

enumerate, evaluate, evaluateAsBoolean, evaluateAsNodeSet, evaluateAsString, getDataType, outputStringValue, selectFirst

Methods inherited from class com.icl.saxon.expr.Expression

containsReferences, display, enumerate, evaluate, evaluateAsBoolean, evaluateAsNodeSet, evaluateAsNumber, evaluateAsString, getDataType, getDependencies, getStaticContext, indent, isContextDocumentNodeSet, make, outputStringValue, reduce, setStaticContext, simplify, usesCurrent

Constructor Details

FilterExpression

public FilterExpression(Expression start,
                        Expression filter)
Constructor
Parameters:
start - A node-set expression denoting the absolute or relative set of nodes from which the navigation path should start.
filter - An expression defining the filter predicate

Method Details

display

public void display(int level)
Diagnostic print of expression structure
Overrides:
display in interface Expression

enumerate

public NodeEnumeration enumerate(Context context,
                                 boolean sort)
            throws XPathException
Evaluate the filter expression in a given context to return a Node Enumeration
Overrides:
enumerate in interface NodeSetExpression
Parameters:
context - the evaluation context
sort - true if the result must be in document order

getDependencies

public int getDependencies()
Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as Context.VARIABLES and Context.CURRENT_NODE
Overrides:
getDependencies in interface Expression

isContextDocumentNodeSet

public boolean isContextDocumentNodeSet()
Determine, in the case of an expression whose data type is Value.NODESET, whether all the nodes in the node-set are guaranteed to come from the same document as the context node. Used for optimization.
Overrides:
isContextDocumentNodeSet in interface Expression

reduce

public Expression reduce(int dep,
                         Context context)
            throws XPathException
Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
Overrides:
reduce in interface Expression
Parameters:
dep - The dependencies to be removed
context - The context to be used for the partial evaluation
Returns:
a new expression that does not have any of the specified dependencies

simplify

public Expression simplify()
            throws XPathException
Simplify an expression
Overrides:
simplify in interface Expression