net.sf.saxon.value
Class SingletonClosure
- Serializable, SequenceIterable, ValueRepresentation
public class SingletonClosure
A SingletonClosure represents a value that has not yet been evaluated: the value is represented
by an expression, together with saved values of all the context variables that the
expression depends on. The value of a SingletonClosure is always either a single item
or an empty sequence.
The expression may depend on local variables and on the context item; these values
are held in the saved XPathContext object that is kept as part of the Closure, and they
will always be read from that object. The expression may also depend on global variables;
these are unchanging, so they can be read from the Bindery in the normal way. Expressions
that depend on other contextual information, for example the values of position(), last(),
current(), current-group(), should not be evaluated using this mechanism: they should
always be evaluated eagerly. This means that the Closure does not need to keep a copy
of these context variables.
Item | asItem() - Return the value in the form of an Item
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int | getLength() - Get the length of the sequence
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Item | itemAt(int n) - Get the n'th item in the sequence (starting from 0).
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SequenceIterator | iterate() - Evaluate the expression in a given context to return an iterator over a sequence
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Value | materialize() - Return a value containing all the items in the sequence returned by this
SequenceIterator
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void | process(XPathContext context) - Process the expression by writing the value to the current Receiver
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asItem , asItem , asIterator , asValue , checkPermittedContents , convertJavaObjectToXPath , convertToJava , convertToJava , effectiveBooleanValue , equals , fromItem , getCanonicalLexicalRepresentation , getCardinality , getItemType , getIterator , getLength , getSchemaComparable , getStringValue , getStringValueCS , itemAt , iterate , iterate , makeQNameValue , process , reduce , stringToNumber , toString |
SingletonClosure
public SingletonClosure(Expression exp,
XPathContext context)
throws XPathException
Constructor should not be called directly, instances should be made using the make() method.
exp
- the expression to be lazily evaluatedcontext
- the context in which the expression should be evaluated
asItem
public Item asItem()
throws XPathException
Return the value in the form of an Item
- asItem in interface Value
- the value in the form of an Item
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
- itemAt in interface Value
materialize
public Value materialize()
throws XPathException
Return a value containing all the items in the sequence returned by this
SequenceIterator
process
public void process(XPathContext context)
throws XPathException
Process the expression by writing the value to the current Receiver
- process in interface Closure
context
- The dynamic context, giving access to the current node,
the current variables, etc.