public class Closure extends Value
This Closure is designed for use when the value is only read once. If the value is read more than once, a new iterator over the underlying expression is obtained each time: this may (for example in the case of a filter expression) involve significant re-calculation.
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.
Modifier and Type | Field and Description |
---|---|
protected int |
depth |
protected Expression |
expression |
protected SequenceIterator |
inputIterator |
protected XPathContextMajor |
savedXPathContext |
EMPTY_CLASS_ARRAY
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
EMPTY_VALUE_ARRAY
Constructor and Description |
---|
Closure()
Constructor should not be called directly, instances should be made using the make() method.
|
Modifier and Type | Method and Description |
---|---|
void |
display(int level,
NamePool pool,
PrintStream out)
Diagnostic display of the expression
|
int |
getCardinality()
Get the cardinality
|
int |
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
|
ItemType |
getItemType(TypeHierarchy th)
Get the static item type
|
int |
getSpecialProperties()
Get the static properties of this expression (other than its type).
|
boolean |
isIndexable()
Determine whether this Closure is indexable
|
SequenceIterator |
iterate(XPathContext context)
Evaluate the expression in a given context to return an iterator over a sequence
|
static Value |
make(Expression expression,
XPathContext context,
int ref)
Construct a Closure by supplying the expression and the set of context variables.
|
static Closure |
makeIteratorClosure(SequenceIterator iterator)
Construct a Closure over an existing SequenceIterator.
|
void |
process(XPathContext context)
Process the instruction, without returning any tail calls
|
Value |
reduce()
Reduce a value to its simplest form.
|
asItem, asIterator, asValue, checkPermittedContents, collapseWhitespace, convert, convertJavaObjectToXPath, convertToJava, effectiveBooleanValue, equals, evaluateAsString, evaluateItem, getDependencies, getIterator, getLength, getParentExpression, getStringValue, hashCode, itemAt, iterateSubExpressions, makeQNameValue, normalizeWhitespace, optimize, promote, schemaEquals, simplify, stringToNumber, toString, trimWhitespace, typeCheck
protected Expression expression
protected XPathContextMajor savedXPathContext
protected int depth
protected SequenceIterator inputIterator
public Closure()
public static Closure makeIteratorClosure(SequenceIterator iterator)
public static Value make(Expression expression, XPathContext context, int ref) throws XPathException
XPathException
public ItemType getItemType(TypeHierarchy th)
getItemType
in interface Expression
getItemType
in class Value
th
- public int getCardinality()
getCardinality
in interface Expression
getCardinality
in class Value
StaticProperty.ALLOWS_ONE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
, StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.ALLOWS_ONE_OR_MORE
, StaticProperty.EMPTY
. This default
implementation returns ZERO_OR_MORE (which effectively gives no
information).public int getSpecialProperties()
getSpecialProperties
in interface Expression
getSpecialProperties
in class Value
StaticProperty.NON_CREATIVE
public int getImplementationMethod()
public SequenceIterator iterate(XPathContext context) throws XPathException
context
- the evaluation context. This is ignored; we use the context saved
as part of the Closure instead.XPathException
- if any dynamic error occurs evaluating the
expressionpublic void process(XPathContext context) throws XPathException
process
in interface Expression
process
in class Value
context
- The dynamic context, giving access to the current node,
the current variables, etc.XPathException
public Value reduce() throws XPathException
reduce
in class Value
XPathException
public boolean isIndexable()
public void display(int level, NamePool pool, PrintStream out)
Value
display
in interface Expression
display
in class Value
level
- indentation level for this expressionpool
- NamePool used to expand any names appearing in the expressionout
- Output destination