net.sf.saxon.expr

Class CardinalityChecker

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
Method Summary
intcomputeCardinality()
Determine the static cardinality of the expression
intcomputeSpecialProperties()
Get the static properties of this expression (other than its type).
StringdisplayOperator(NamePool pool)
Diagnostic print of expression structure
booleanequals(Object other)
Is this expression the same as another expression?
ItemevaluateItem(XPathContext context)
Evaluate as an Item.
intgetImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible
intgetRequiredCardinality()
Get the required cardinality
SequenceIteratoriterate(XPathContext context)
Iterate over the sequence of values
static ComputedExpressionmakeCardinalityChecker(Expression sequence, int cardinality, RoleLocator role)
Factory method to construct a CardinalityChecker.
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
voidprocess(XPathContext context)
Process the instruction, without returning any tail calls
voidsetErrorCode(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)
ExpressiontypeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression

Method Detail

computeCardinality

public int computeCardinality()
Determine the static cardinality of the expression

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.

displayOperator

public String displayOperator(NamePool pool)
Diagnostic print of expression structure

equals

public boolean equals(Object other)
Is this expression the same as another expression?

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate as an Item.

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.

getItemType

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

Parameters: th

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

iterate

public SequenceIterator iterate(XPathContext context)
Iterate over the sequence of values

makeCardinalityChecker

public static ComputedExpression 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 cardinality role

Returns: a new Expression that does the CardinalityChecking (not necessarily a CardinalityChecker)

optimize

public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
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.

Parameters: opt the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances. env the static context of the expression 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 ITEM_TYPE

Returns: the original expression, rewritten if appropriate to optimize execution

Throws: net.sf.saxon.trans.StaticError if an error is discovered during this phase (typically a type error)

process

public void process(XPathContext context)
Process the instruction, without returning any tail calls

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)

typeCheck

public Expression typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression