java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.FilterExpression

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, org.xml.sax.Locator
```
public final class FilterExpression
extends Expression
```
A FilterExpression contains a base expression and a filter predicate, which may be an integer expression (positional filter), or a boolean expression (qualifier)

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field Description

static int FILTERED
- Fields inherited from class net.sf.saxon.expr.Expression
  EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties

Constructor Summary

Constructors
Constructor Description

FilterExpression(Expression start, Expression filter)
Constructor

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`PathMap.PathMapNodeSet`	`addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)`	Add a representation of this expression to a PathMap.
`int`	`computeCardinality()`	Get the static cardinality of this expression
`int`	`computeDependencies()`	Determine which aspects of the context the expression depends on.
`int`	`computeSpecialProperties()`	Get the static properties of this expression (other than its type).
`Expression`	`copy()`	Copy an expression.
`boolean`	`equals(java.lang.Object other)`	Is this expression the same as another expression?
`void`	`explain(ExpressionPresenter out)`	Diagnostic print of expression structure.
`Expression`	`getBaseExpression()`	Get the underlying expression
`Expression`	`getFilter()`	Get the filter expression
`ItemType`	`getItemType(TypeHierarchy th)`	Get the data type of the items returned
`int`	`hashCode()`	get HashCode for comparing two expressions
`boolean`	`hasLoopingSubexpression(Expression child)`	Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly
`boolean`	`isIndependentNumericFilter()`	Determine whether the filter is a simple independent numeric, that is, an expression that satisfies the following conditions: (a) its value is numeric; (b) the value does not depend on the context item or position; (c) the cardinality is zero or one.
`boolean`	`isPositional(TypeHierarchy th)`	Determine if the filter is positional
`boolean`	`isSimpleBooleanFilter()`	Test if the filter always returns a singleton boolean
`SequenceIterator`	`iterate(XPathContext context)`	Iterate over the results, returning them in the correct order
`java.util.Iterator`	`iterateSubExpressions()`	Get the immediate subexpressions of this expression
`Expression`	`optimize(ExpressionVisitor visitor, ItemType contextItemType)`	Perform optimisation of an expression and its subexpressions.
`Expression`	`promote(PromotionOffer offer)`	Promote this expression if possible
`boolean`	`replaceSubExpression(Expression original, Expression replacement)`	Replace one subexpression by a replacement subexpression
`Expression`	`simplify(ExpressionVisitor visitor)`	Simplify an expression
`java.lang.String`	`toString()`	The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
`Expression`	`typeCheck(ExpressionVisitor visitor, ItemType contextItemType)`	Type-check the expression

Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, 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

- Field Detail
  - FILTERED
```
public static final int FILTERED
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - 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 Detail
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Get the data type of the items returned
    
    Specified by:
    
    getItemType in class Expression
    
    Parameters:
    
    th - the type hierarchy cache
    
    Returns:
    
    an integer representing the data type
  - getBaseExpression
```
public Expression getBaseExpression()
```
    Get the underlying expression
    
    Returns:
    
    the expression being filtered
  - getFilter
```
public Expression getFilter()
```
    Get the filter expression
    
    Returns:
    
    the expression acting as the filter predicate
  - isPositional
```
public boolean isPositional(TypeHierarchy th)
```
    Determine if the filter is positional
    
    Parameters:
    
    th - the Type Hierarchy (for cached access to type information)
    
    Returns:
    
    true if the value of the filter depends on the position of the item against which it is evaluated
  - isSimpleBooleanFilter
```
public boolean isSimpleBooleanFilter()
```
    Test if the filter always returns a singleton boolean
    
    Returns:
    
    true if the filter is a simple boolean expression
  - isIndependentNumericFilter
```
public boolean isIndependentNumericFilter()
```
    Determine whether the filter is a simple independent numeric, that is, an expression that satisfies the following conditions: (a) its value is numeric; (b) the value does not depend on the context item or position; (c) the cardinality is zero or one.
    
    Returns:
    
    true if the filter is a numeric value that does not depend on the context item or position
  - simplify
```
public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
```
    Simplify an expression
    
    Overrides:
    
    simplify in class Expression
    
    Parameters:
    
    visitor - the expression visitor
    
    Returns:
    
    the simplified expression
    
    Throws:
    
    XPathException - if any failure occurs
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
```
    Type-check the expression
    
    Overrides:
    
    typeCheck in class Expression
    
    Parameters:
    
    visitor - the expression visitor
    
    contextItemType - the type of the context item for this expression
    
    Returns:
    
    the expression after type-checking (potentially modified to add run-time checks and/or conversions)
    
    Throws:
    
    XPathException - if an error is discovered during this phase (typically a type error)
  - optimize
```
public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
                    throws XPathException
```
    Perform optimisation of an expression and its subexpressions.
    
    This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
    
    Overrides:
    
    optimize in class Expression
    
    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)
  - 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.
    
    Overrides:
    
    addToPathMap in class 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
  - promote
```
public Expression promote(PromotionOffer offer)
                   throws XPathException
```
    Promote this expression if possible
    
    Overrides:
    
    promote in class Expression
    
    Parameters:
    
    offer - details of the promotion that is possible
    
    Returns:
    
    the promoted expression (or the original expression, unchanged)
    
    Throws:
    
    XPathException - if any error is detected
  - iterateSubExpressions
```
public java.util.Iterator iterateSubExpressions()
```
    Get the immediate subexpressions of this expression
    
    Overrides:
    
    iterateSubExpressions in class Expression
    
    Returns:
    
    the subexpressions, as an array
  - hasLoopingSubexpression
```
public boolean hasLoopingSubexpression(Expression child)
```
    Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly
    
    Overrides:
    
    hasLoopingSubexpression in class Expression
    
    Parameters:
    
    child - the immediate subexpression
    
    Returns:
    
    true if the child expression is evaluated repeatedly
  - replaceSubExpression
```
public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
```
    Replace one subexpression by a replacement subexpression
    
    Overrides:
    
    replaceSubExpression in class Expression
    
    Parameters:
    
    original - the original subexpression
    
    replacement - the replacement subexpression
    
    Returns:
    
    true if the original subexpression is found
  - computeCardinality
```
public int computeCardinality()
```
    Get the static cardinality of this expression
    
    Specified by:
    
    computeCardinality in class Expression
    
    Returns:
    
    the cardinality. The method attempts to determine the case where the filter predicate is guaranteed to select at most one item from the sequence being filtered
  - computeSpecialProperties
```
public int computeSpecialProperties()
```
    Get the static properties of this expression (other than its type). The result is bit-significant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
    
    Overrides:
    
    computeSpecialProperties in class Expression
    
    Returns:
    
    the static properties of the expression, as a bit-significant value
  - equals
```
public boolean equals(java.lang.Object other)
```
    Is this expression the same as another expression?
    
    Overrides:
    
    equals in class java.lang.Object
    
    Parameters:
    
    other - the expression to be compared with this one
    
    Returns:
    
    true if the two expressions are statically equivalent
  - hashCode
```
public int hashCode()
```
    get HashCode for comparing two expressions
    
    Overrides:
    
    hashCode in class java.lang.Object
    
    Returns:
    
    the hash code
  - iterate
```
public SequenceIterator iterate(XPathContext context)
                         throws XPathException
```
    Iterate over the results, returning them in the correct order
    
    Specified by:
    
    iterate in interface SequenceIterable
    
    Overrides:
    
    iterate in class Expression
    
    Parameters:
    
    context - the dynamic context for the evaluation
    
    Returns:
    
    an iterator over the expression results
    
    Throws:
    
    XPathException - if any dynamic error occurs
  - computeDependencies
```
public int computeDependencies()
```
    Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE
    
    Overrides:
    
    computeDependencies in class Expression
    
    Returns:
    
    the dependencies
  - 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
  - toString
```
public java.lang.String toString()
```
    The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
    
    Overrides:
    
    toString in class Expression
  - explain
```
public void explain(ExpressionPresenter out)
```
    Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
    
    Specified by:
    
    explain in class Expression
    
    Parameters:
    
    out - the ExpressionPresenter to be used

Class FilterExpression

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Field Detail

FILTERED

Constructor Detail

FilterExpression

Method Detail

getItemType

getBaseExpression

getFilter

isPositional

isSimpleBooleanFilter

isIndependentNumericFilter

simplify

typeCheck

optimize

addToPathMap

promote

iterateSubExpressions

hasLoopingSubexpression

replaceSubExpression

computeCardinality

computeSpecialProperties

equals

hashCode

iterate

computeDependencies

copy

toString

explain