net.sf.saxon.expr
public class LetExpression extends Assignation implements TailCallReturner, DivisibleInstruction
Field Summary | |
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int | evaluationMode |
int | refCount |
Constructor Summary | |
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LetExpression()
Create a LetExpression |
Method Summary | |
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void | addReference(boolean isLoopingReference)
Register a variable reference that refers to the variable bound in this let expression |
void | checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole)
Check that any elements and attributes constructed or returned by this expression are acceptable
in the content model of a given complex type. |
int | computeCardinality()
Determine the static cardinality of the expression |
int | computeSpecialProperties()
Get the static properties of this expression (other than its type). |
Expression | copy()
Copy an expression. |
boolean | effectiveBooleanValue(XPathContext context)
Get the effective boolean value of the expression. |
protected ValueRepresentation | eval(XPathContext context)
Evaluate the variable. |
Item | evaluateItem(XPathContext context)
Evaluate the expression as a singleton |
void | evaluatePendingUpdates(XPathContext context, PendingUpdateList pul)
Evaluate an updating expression, adding the results to a Pending Update List.
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void | explain(ExpressionPresenter out)
Diagnostic print of expression structure. |
ItemType | getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible
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int | getNominalReferenceCount()
Get the (nominal) count of the number of references to this variable |
boolean | implementsStaticTypeCheck()
Determine whether this expression implements its own method for static type checking
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boolean | isIndexedVariable()
Test whether the variable bound by this let expression should be indexable |
boolean | isVacuousExpression()
Determine whether this is a vacuous expression as defined in the XQuery update specification |
SequenceIterator | iterate(XPathContext context)
Iterate over the result of the expression to return a sequence of items |
EventIterator | iterateEvents(XPathContext context)
Iterate over the result of the expression to return a sequence of events |
int | markTailFunctionCalls(StructuredQName qName, int arity)
Mark tail function calls |
Expression | optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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void | process(XPathContext context)
Process this expression as an instruction, writing results to the current
outputter |
TailCall | processLeavingTail(XPathContext context)
ProcessLeavingTail: called to do the real work of this instruction.
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void | processLeft(Stack<XPathContext> contextStack, Stack state)
In streaming mode, process the first half of the instruction (for example, to start a new document or element) |
void | processRight(Stack<XPathContext> contextStack, Stack state)
In streaming mode, process the second half of the instruction (for example, to end a new document or element) |
Expression | promote(PromotionOffer offer, Expression parent)
Promote this expression if possible |
void | setEvalBeforeChildren(boolean before)
When streaming, set whether the variable is evaluated before processing children or after |
void | setIndexedVariable()
Indicate that the variable bound by this let expression should be indexable
(because it is used in an appropriate filter expression) |
Expression | staticTypeCheck(SequenceType req, boolean backwardsCompatible, RoleLocator role, ExpressionVisitor visitor)
Static type checking for let expressions is delegated to the expression itself,
and is performed on the "action" expression, to allow further delegation to the branches
of a conditional |
String | toString()
The toString() method for an expression attempts to give a representation of the expression
in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
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Expression | typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression. |
Parameters: isLoopingReference - true if the reference occurs within a loop, such as the predicate of a filter expression
Returns: the copy of the original expression
Parameters: context The context in which the expression is to be evaluated
Returns: the effective boolean value
Throws: net.sf.saxon.trans.XPathException if any dynamic error occurs evaluating the expression
Parameters: context the dynamic evaluation context
Returns: the result of evaluating the expression that is bound to the variable
Parameters: context the XPath dynamic evaluation context pul the pending update list to which the results should be written
Parameters: th the type hierarchy cache
Returns: one of the values Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
Returns: zero if there are no references, one if there is a single reference that is not in a loop, some higher number if there are multiple references (or a single reference in a loop), or the special value @link RangeVariable#FILTERED} if there are any references in filter expressions that require searching.
Returns: true - this expression has a non-trivial implementation of the staticTypeCheck() method
Returns: true if the variable should be indexable
Returns: true if this expression is vacuous
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
Parameters: visitor an expression visitor contextItemType 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 ITEM_TYPE
Returns: the original expression, rewritten if appropriate to optimize execution
Throws: XPathException if an error is discovered during this phase (typically a type error)
Parameters: context The dynamic context of the transformation, giving access to the current node, the current variables, etc.
Returns: null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
Parameters: contextStack state a stack on which the instruction can save state information during the call on processLeft()
Parameters: contextStack state a stack on which the instruction can save state information during the call on processLeft()
Parameters: before true if the initializer should be evaluated during the processLeft() call
Parameters: req the required type backwardsCompatible true if backwards compatibility mode applies role the role of the expression in relation to the required type visitor an expression visitor
Returns: the expression after type checking (perhaps augmented with dynamic type checking code)
Throws: XPathException if failures occur, for example if the static type of one branch of the conditional is incompatible with the required type
Returns: a representation of the expression as a string