net.sf.saxon.expr
Class CardinalityChecker

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.CardinalityChecker

All Implemented Interfaces:

Expression, MappingFunction, java.io.Serializable

public final class CardinalityChecker

extends ComputedExpression

implements MappingFunction

A CardinalityChecker implements the cardinality checking of "treat as": that is, it returns the supplied sequence, checking that its cardinality is correct

See Also:

Serialized Form

Field Summary

 

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

lineNumber, NO_ARGUMENTS, staticProperties

 

Constructor Summary

CardinalityChecker(Expression sequence, int cardinality, RoleLocator role)           Constructor

 

Method Summary
Expression	analyze(StaticContext env)           Type-check the expression
int	computeCardinality()           Determine the static cardinality of the expression
int	computeSpecialProperties()           Get the static properties of this expression (other than its type).
void	display(int level, NamePool pool)           Diagnostic print of expression structure
Item	evaluateItem(XPathContext context)           Evaluate as an Item.
ItemType	getItemType()           Determine the data type of the items returned by the expression, if possible
Expression[]	getSubExpressions()           Get the immediate subexpressions of this expression
SequenceIterator	iterate(XPathContext context)           Iterate over the sequence of values
java.lang.Object	map(Item item, XPathContext context, java.lang.Object info)           Mapping function: this is used only if the expression does not allow a sequence of more than one item.
Expression	promote(PromotionOffer offer)           Promote this expression if possible
Expression	simplify()           Simplify an expression

 

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

computeDependencies, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSourceLocator, getSpecialProperties, markTailFunctionCalls, setLineNumber, typeError

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Constructor Detail

CardinalityChecker

public CardinalityChecker(Expression sequence,
                          int cardinality,
                          RoleLocator role)

Constructor

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Specified by:

simplify in interface Expression

Overrides:

simplify in class ComputedExpression

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

analyze

public Expression analyze(StaticContext env)
                   throws XPathException

Type-check the expression

Specified by:

analyze in interface Expression

Parameters:

env - the static context of the expression

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

XPathException

promote

public Expression promote(PromotionOffer offer)
                   throws XPathException

Promote this expression if possible

Specified by:

promote in interface Expression

Overrides:

promote in class ComputedExpression

Parameters:

offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression

Returns:

if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression

Throws:

XPathException - if any error is detected

getSubExpressions

public Expression[] getSubExpressions()

Get the immediate subexpressions of this expression

Specified by:

getSubExpressions in interface Expression

Overrides:

getSubExpressions in class ComputedExpression

Returns:

an array containing the sub-expressions of this expression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Iterate over the sequence of values

Specified by:

iterate in interface Expression

Overrides:

iterate in class ComputedExpression

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

map

public java.lang.Object map(Item item,
                            XPathContext context,
                            java.lang.Object info)
                     throws XPathException

Mapping function: this is used only if the expression does not allow a sequence of more than one item.

Specified by:

map in interface MappingFunction

Parameters:

item - The item to be mapped. If context is supplied, this must be the same as context.currentItem().

context - The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.

info - Arbitrary information supplied by the creator of the MappingIterator. It must be read-only and immutable for the duration of the iteration.

Returns:

either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate as an Item.

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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()

Determine the data type of the items returned by the expression, if possible

Specified by:

getItemType in interface Expression

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

Specified by:

computeCardinality in class ComputedExpression

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. 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 ComputedExpression

display

public void display(int level,
                    NamePool pool)

Diagnostic print of expression structure

Specified by:

display in interface Expression

Parameters:

level - indentation level for this expression