net.sf.saxon.expr

Class InstanceOfExpression

public final class InstanceOfExpression extends UnaryExpression implements MappingExpression

InstanceOf Expression: implements "Expr instance of data-type"
Field Summary
inttargetCardinality
ItemTypetargetType
Constructor Summary
InstanceOfExpression(Expression source, SequenceType target)
Construct an "instance of" expression in the form "source instance of target"
Method Summary
intcomputeCardinality()
Determine the cardinality
Expressioncopy()
Copy an expression.
booleaneffectiveBooleanValue(XPathContext context)
Evaluate the expression as a boolean
booleanequals(Object other)
Is this expression the same as another expression?
ItemevaluateItem(XPathContext context)
Evaluate the expression
voidexplain(ExpressionPresenter destination)
Diagnostic print of expression structure.
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the result of the InstanceOf expression
SequenceIteratorgetMappingIterator(SequenceIterator base, XPathContext context)
Return an iterator over the results of the expression, given an iterator over the principal operand to the expression
intgetRequiredCardinality()
Get the cardinality that we are testing for membership of
ItemTypegetRequiredItemType()
Get the item type that we are testing for membership of
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
ExpressiontypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

Field Detail

targetCardinality

int targetCardinality

targetType

ItemType targetType

Constructor Detail

InstanceOfExpression

public InstanceOfExpression(Expression source, SequenceType target)
Construct an "instance of" expression in the form "source instance of target"

Parameters: source the expression whose type is to be tested target the type against which it is tested

Method Detail

computeCardinality

public int computeCardinality()
Determine the cardinality

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
Evaluate the expression as a boolean

equals

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

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the expression

explain

public void explain(ExpressionPresenter destination)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the result of the InstanceOf expression

Parameters: th the type hierarchy cache

getMappingIterator

public SequenceIterator getMappingIterator(SequenceIterator base, XPathContext context)
Return an iterator over the results of the expression, given an iterator over the principal operand to the expression

Parameters: base an interator over the input to the expression context dynamic evaluation context

Returns: an iterator over the results of the expression

Throws: XPathException

getRequiredCardinality

public int getRequiredCardinality()
Get the cardinality that we are testing for membership of

Returns: the required cardinality

getRequiredItemType

public ItemType getRequiredItemType()
Get the item type that we are testing for membership of

Returns: the item type

optimize

public Expression optimize(ExpressionVisitor visitor, 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: 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 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)

typeCheck

public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

Returns: the checked expression