net.sf.saxon.expr
Class CastableExpression

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.UnaryExpression
              |
              +--net.sf.saxon.expr.CastableExpression
All Implemented Interfaces:
Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

public final class CastableExpression
extends UnaryExpression

Castable Expression: implements "Expr castable as atomic-type?". The implementation simply wraps a cast expression with a try/catch.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
CastableExpression(Expression source, AtomicType target, boolean allowEmpty)
           
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Type-check the expression
 int computeCardinality()
          Determine the static cardinality.
protected  java.lang.String displayOperator(NamePool pool)
          Give a string representation of the operator for use in diagnostics
 boolean effectiveBooleanValue(XPathContext context)
          Get the effective boolean value of the expression.
 boolean equals(java.lang.Object other)
          Is this expression the same as another expression?
 Item evaluateItem(XPathContext context)
          Evaluate the expression
 ItemType getItemType()
          Determine the data type of the result of the Castable expression
 Expression simplify(StaticContext env)
          Simplify the expression
 
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeSpecialProperties, display, getBaseExpression, hashCode, iterateSubExpressions, promote
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeStaticProperties, dynamicError, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CastableExpression

public CastableExpression(Expression source,
                          AtomicType target,
                          boolean allowEmpty)
Method Detail

simplify

public Expression simplify(StaticContext env)
                    throws XPathException
Simplify the expression

Specified by:
simplify in interface Expression
Overrides:
simplify in class UnaryExpression
Returns:
the simplified expression
XPathException

analyze

public Expression analyze(StaticContext env,
                          ItemType contextItemType)
                   throws XPathException
Type-check the expression

Specified by:
analyze in interface Expression
Overrides:
analyze in class UnaryExpression
Parameters:
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 Type.ITEM_TYPE
Returns:
the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
XPathException

equals

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

Overrides:
equals in class UnaryExpression

getItemType

public ItemType getItemType()
Determine the data type of the result of the Castable expression

Specified by:
getItemType in interface Expression
Overrides:
getItemType in class UnaryExpression
Returns:
the item type of the items in the result sequence, insofar as this is known statically.

computeCardinality

public int computeCardinality()
Description copied from class: UnaryExpression
Determine the static cardinality. Default implementation returns the cardinality of the operand

Overrides:
computeCardinality in class UnaryExpression

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the expression

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

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
Description copied from class: ComputedExpression
Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.

Specified by:
effectiveBooleanValue in interface Expression
Overrides:
effectiveBooleanValue in class ComputedExpression
Parameters:
context - The context in which the expression is to be evaluated
Returns:
the effective boolean value

displayOperator

protected java.lang.String displayOperator(NamePool pool)
Give a string representation of the operator for use in diagnostics

Specified by:
displayOperator in class UnaryExpression
Returns:
the operator, as a string