net.sf.saxon.expr
Class CastAsQName

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.CastAsQName
All Implemented Interfaces:
Expression, java.io.Serializable

public class CastAsQName
extends ComputedExpression

This class supports casting a string to a QName

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
lineNumber, NO_ARGUMENTS, staticProperties
 
Constructor Summary
CastAsQName(Expression s)
           
 
Method Summary
 Expression analyze(StaticContext env)
          Perform static analysis of an expression and its subexpressions.
 int computeCardinality()
           
 void display(int level, NamePool pool)
          Diagnostic print of expression structure.
 Item evaluateItem(XPathContext context)
          Evaluate an expression as a single item.
 int getIntrinsicDependencies()
          Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
 ItemType getItemType()
          Determine the data type of the expression, if possible.
 Expression[] getSubExpressions()
          Get the immediate sub-expressions of this expression.
 Expression promote(PromotionOffer offer)
          Offer promotion for this subexpression.
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getLineNumber, getSpecialProperties, iterate, markTailFunctionCalls, setLineNumber, simplify, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CastAsQName

public CastAsQName(Expression s)
Method Detail

analyze

public Expression analyze(StaticContext env)
                   throws XPathException
Description copied from interface: Expression
Perform static analysis of an expression and its subexpressions.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables will only be accurately known if they have been explicitly declared.

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
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

promote

public Expression promote(PromotionOffer offer)
                   throws XPathException
Description copied from class: ComputedExpression
Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

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

computeCardinality

public int computeCardinality()
Specified by:
computeCardinality in class ComputedExpression

getItemType

public ItemType getItemType()
Description copied from interface: Expression
Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

Returns:
a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

getIntrinsicDependencies

public int getIntrinsicDependencies()
Description copied from class: ComputedExpression
Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".

Overrides:
getIntrinsicDependencies in class ComputedExpression
Returns:
a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

getSubExpressions

public Expression[] getSubExpressions()
Description copied from class: ComputedExpression
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Specified by:
getSubExpressions in interface Expression
Overrides:
getSubExpressions in class ComputedExpression
Returns:
an array containing the sub-expressions of this expression

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Description copied from class: ComputedExpression
Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.

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

display

public void display(int level,
                    NamePool pool)
Description copied from interface: Expression
Diagnostic print of expression structure. The expression is written to the System.err output stream

Parameters:
level - indentation level for this expression