net.sf.saxon.expr

Class CardinalityChecker

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator

public final class CardinalityChecker
extends UnaryExpression

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

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, PROCESS_METHOD, locationId, staticProperties

Method Summary

int
computeCardinality()
Determine the static cardinality of the expression
int
computeSpecialProperties()
Get the static properties of this expression (other than its type).
Expression
copy()
Copy an expression.
static String
depictSequenceStart(SequenceIterator seq, int max)
Show the first couple of items in a sequence in an error message
boolean
equals(Object other)
Is this expression the same as another expression?
Item
evaluateItem(XPathContext context)
Evaluate as an Item.
void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.
int
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible
int
getRequiredCardinality()
Get the required cardinality
RoleLocator
getRoleLocator()
Get the RoleLocator, which contains diagnostic information for use if the cardinality check fails
SequenceIterator
iterate(XPathContext context)
Iterate over the sequence of values
static Expression
makeCardinalityChecker(Expression sequence, int cardinality, RoleLocator role)
Factory method to construct a CardinalityChecker.
Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
void
process(XPathContext context)
Process the instruction, without returning any tail calls
void
setErrorCode(String code)
Set the error code to be returned (this is used when evaluating the functions such as exactly-one() which have their own error codes)
Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

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

computeCardinality, computeSpecialProperties, displayExpressionName, displayOperator, equals, explain, getBaseExpression, getItemType, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Method Details

computeCardinality

public int computeCardinality()
Determine the static cardinality of the expression
Overrides:
computeCardinality in interface UnaryExpression

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 interface UnaryExpression

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

depictSequenceStart

public static String depictSequenceStart(SequenceIterator seq,
                                         int max)
Show the first couple of items in a sequence in an error message
Parameters:
seq - iterator over the sequence
max - maximum number of items to be shown
Returns:
a message display of the contents of the sequence

equals

public boolean equals(Object other)
Is this expression the same as another expression?
Overrides:
equals in interface UnaryExpression

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate as an Item.
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface Expression

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
Overrides:
explain in interface UnaryExpression

getImplementationMethod

public int getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided. This implementation provides both iterate() and process() methods natively.
Overrides:
getImplementationMethod in interface Expression

getItemType

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

getRequiredCardinality

public int getRequiredCardinality()
Get the required cardinality
Returns:
the cardinality required by this checker

getRoleLocator

public RoleLocator getRoleLocator()
Get the RoleLocator, which contains diagnostic information for use if the cardinality check fails
Returns:
the diagnostic information

iterate

public SequenceIterator iterate(XPathContext context)
            throws XPathException
Iterate over the sequence of values
Specified by:
iterate in interface SequenceIterable
Overrides:
iterate in interface Expression

makeCardinalityChecker

public static Expression makeCardinalityChecker(Expression sequence,
                                                int cardinality,
                                                RoleLocator role)
Factory method to construct a CardinalityChecker. The method may create an expression that combines the cardinality checking with the functionality of the underlying expression class
Parameters:
sequence - the base sequence whose cardinality is to be checked
cardinality - the required cardinality
role - information to be used in error reporting
Returns:
a new Expression that does the CardinalityChecking (not necessarily a CardinalityChecker)

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 interface 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 if appropriate to optimize execution
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

process

public void process(XPathContext context)
            throws XPathException
Process the instruction, without returning any tail calls
Overrides:
process in interface Expression
Parameters:
context - The dynamic context, giving access to the current node, the current variables, etc.

setErrorCode

public void setErrorCode(String code)
Set the error code to be returned (this is used when evaluating the functions such as exactly-one() which have their own error codes)
Parameters:
code - the error code to be used

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression
Overrides:
typeCheck in interface UnaryExpression