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java.lang.Object | +--net.sf.saxon.expr.ComputedExpression | +--net.sf.saxon.expr.Assignation | +--net.sf.saxon.expr.LetExpression
A LetExpression is modelled on the XQuery syntax let $x := expr return expr. This syntax is not available in the surface XPath language, but it is used internally in an optimized expression tree.
Field Summary |
Fields inherited from class net.sf.saxon.expr.Assignation |
action, declaration, nameCode, sequence, slotNumber, variableName |
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 | |
LetExpression()
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Method Summary | |
Expression |
analyze(StaticContext env,
ItemType contextItemType)
Type-check the expression |
int |
computeCardinality()
Determine the static cardinality of the expression |
int |
computeSpecialProperties()
Get the static properties of this expression (other than its type). |
void |
display(int level,
NamePool pool,
java.io.PrintStream out)
Diagnostic print of expression structure |
protected Value |
eval(XPathContext context)
Evaluate the variable. |
Item |
evaluateItem(XPathContext context)
Evaluate the expression as a singleton |
ItemType |
getItemType()
Determine the data type of the items returned by the expression, if possible |
SequenceIterator |
iterate(XPathContext context)
Iterate over the sequence of values |
boolean |
markTailFunctionCalls()
Mark tail function calls |
void |
process(XPathContext context)
Process this expression as an instruction, writing results to the current outputter |
Expression |
promote(PromotionOffer offer)
Promote this expression if possible |
Methods inherited from class net.sf.saxon.expr.Assignation |
evaluateVariable, getVariableFingerprint, getVariableName, getVariableNameCode, iterateSubExpressions, setAction, setSequence, setSlotNumber, setVariableDeclaration, simplify |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public LetExpression()
Method Detail |
public Expression analyze(StaticContext env, ItemType contextItemType) throws XPathException
env
- the static context of the expressioncontextItemType
- 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
XPathException
public SequenceIterator iterate(XPathContext context) throws XPathException
iterate
in interface Expression
iterate
in class ComputedExpression
context
- supplies the context for evaluation
XPathException
- if any dynamic error occurs evaluating the
expressionprotected Value eval(XPathContext context) throws XPathException
XPathException
public Item evaluateItem(XPathContext context) throws XPathException
evaluateItem
in interface Expression
evaluateItem
in class ComputedExpression
context
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expressionpublic void process(XPathContext context) throws XPathException
process
in interface Expression
process
in class ComputedExpression
context
- The dynamic context, giving access to the current node,
the current variables, etc.
XPathException
public ItemType getItemType()
public int computeCardinality()
computeCardinality
in class ComputedExpression
public int computeSpecialProperties()
computeSpecialProperties
in class ComputedExpression
public boolean markTailFunctionCalls()
markTailFunctionCalls
in class ComputedExpression
public Expression promote(PromotionOffer offer) throws XPathException
promote
in interface Expression
promote
in class Assignation
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
XPathException
- if any error is detectedpublic void display(int level, NamePool pool, java.io.PrintStream out)
level
- indentation level for this expressionpool
- NamePool used to expand any names appearing in the expressionout
- Output destination
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