net.sf.saxon.value
Class SequenceValue

java.lang.Object
  |
  +--net.sf.saxon.value.Value
        |
        +--net.sf.saxon.value.SequenceValue
All Implemented Interfaces:
Expression, java.io.Serializable
Direct Known Subclasses:
Closure, EmptySequence, SequenceExtent, SequenceIntent

public abstract class SequenceValue
extends Value

A SequenceValue object represents a sequence whose members are all AtomicValues or Nodes.

See Also:
Serialized Form

Field Summary
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
SequenceValue()
           
 
Method Summary
 java.lang.Object convertToJava(java.lang.Class target, Configuration config, XPathContext context)
          Convert to Java object (for passing to external functions)
 void display(int level, NamePool pool, java.io.PrintStream out)
          Diagnostic display of the expression
 boolean effectiveBooleanValue(XPathContext context)
          Get the effective boolean value of the expression.
 boolean equals(java.lang.Object obj)
          Compare two sequence values for equality.
 java.lang.String evaluateAsString(XPathContext context)
          Evaluate an expression as a String.
 Item evaluateItem(XPathContext context)
          Evaluate as a singleton item (or empty sequence)
 int getCardinality()
          Determine the cardinality
 int getImplementationMethod()
          An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
 ItemType getItemType()
          Determine the data type of the items in the expression, if possible
 java.lang.String getStringValue()
          Convert the value to a string, using the serialization rules.
 int hashCode()
          Return a hash code to support the equals() function
 Item itemAt(int n)
          Get the n'th item in the sequence (starting from 0).
 SequenceExtent materialize()
          Materialize the SequenceValue as a SequenceExtent
 void process(XPathContext context)
          Process the instruction, without returning any tail calls
 
Methods inherited from class net.sf.saxon.value.Value
analyze, asItem, asValue, collapseWhitespace, convertJavaObjectToXPath, getDependencies, getParentExpression, getSpecialProperties, inverse, iterateSubExpressions, normalizeWhitespace, promote, simplify, stringToNumber, toString, trimWhitespace
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface net.sf.saxon.expr.Expression
iterate
 

Constructor Detail

SequenceValue

public SequenceValue()
Method Detail

materialize

public SequenceExtent materialize()
                           throws XPathException
Materialize the SequenceValue as a SequenceExtent

XPathException

getImplementationMethod

public final 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 prefered.


process

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

Parameters:
context - The dynamic context, giving access to the current node, the current variables, etc.
XPathException

getItemType

public ItemType getItemType()
Determine the data type of the items in the expression, if possible

Returns:
AnyItemType (not known)

getCardinality

public int getCardinality()
Determine the cardinality

Returns:
one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

itemAt

public Item itemAt(int n)
            throws XPathException
Get the n'th item in the sequence (starting from 0). This is defined for all SequenceValues, but its real benefits come for a SequenceValue stored extensionally

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate as a singleton item (or empty sequence)

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

getStringValue

public java.lang.String getStringValue()
                                throws XPathException
Convert the value to a string, using the serialization rules. For atomic values this is the same as a cast; for sequence values it gives a space-separated list.

Specified by:
getStringValue in class Value
Throws:
XPathException - The method can fail if evaluation of the value has been deferred, and if a failure occurs during the deferred evaluation. No failure is possible in the case of an AtomicValue.

evaluateAsString

public java.lang.String evaluateAsString(XPathContext context)
                                  throws XPathException
Evaluate an expression as a String. This function must only be called in contexts where it is known that the expression will return a single string (or where an empty sequence is to be treated as a zero-length string). Implementations should not attempt to convert the result to a string, other than converting () to "". This method is used mainly to evaluate expressions produced by compiling an attribute value template.

Parameters:
context - The context in which the expression is to be evaluated
Returns:
the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".
Throws:
XPathException - if any dynamic error occurs evaluating the expression
java.lang.ClassCastException - if the result type of the expression is not xs:string?

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
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.

Parameters:
context - The context in which the expression is to be evaluated
Returns:
the effective boolean value
Throws:
XPathException - if any dynamic error occurs evaluating the expression

equals

public boolean equals(java.lang.Object obj)
Compare two sequence values for equality. This supports identity constraints in XML Schema, which allow list-valued elements and attributes to participate in key and uniqueness constraints. This method returns false if any error occurs during the comparison, or if any of the items in either sequence is a node rather than an atomic value.

Overrides:
equals in class java.lang.Object

hashCode

public int hashCode()
Return a hash code to support the equals() function

Overrides:
hashCode in class java.lang.Object

convertToJava

public java.lang.Object convertToJava(java.lang.Class target,
                                      Configuration config,
                                      XPathContext context)
                               throws XPathException
Convert to Java object (for passing to external functions)

Specified by:
convertToJava in class Value
Parameters:
target - The class required by the external function
config - The configuration (needed for access to schema information)
Returns:
an object of the target class
XPathException

display

public void display(int level,
                    NamePool pool,
                    java.io.PrintStream out)
Diagnostic display of the expression

Parameters:
level - indentation level for this expression
pool - NamePool used to expand any names appearing in the expression
out - Output destination