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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.IsLastExpression
public final class IsLastExpression
A position() eq last() expression, generated by the optimizer.
Field Summary |
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Fields inherited from class net.sf.saxon.expr.Expression |
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EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD |
Constructor Summary | |
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IsLastExpression(boolean condition)
Construct a condition that tests position() eq last() (if condition is true) or position() ne last() (if condition is false). |
Method Summary | |
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int |
computeCardinality()
Determine the static cardinality |
int |
computeSpecialProperties()
Determine the special properties of this expression |
Expression |
copy()
Copy an expression. |
Item |
evaluateItem(XPathContext c)
Evaluate an expression as a single item. |
void |
explain(ExpressionPresenter destination)
Diagnostic print of expression structure. |
boolean |
getCondition()
Get the condition we are testing for |
int |
getIntrinsicDependencies()
Get the dependencies of this expression on the context |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the expression |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform type checking of an expression and its subexpressions. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public IsLastExpression(boolean condition)
condition
- true if we are testing "equals", false for "not equals".Method Detail |
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public boolean getCondition()
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Expression
This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.
typeCheck
in class Expression
visitor
- an expression visitorcontextItemType
- 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
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Expression
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.
optimize
in class Expression
visitor
- an expression visitorcontextItemType
- 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
public int computeSpecialProperties()
computeSpecialProperties
in class Expression
StaticProperty.NON_CREATIVE
.public Item evaluateItem(XPathContext c) throws XPathException
Expression
evaluateItem
in class Expression
c
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expressionpublic ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
public int computeCardinality()
computeCardinality
in class Expression
StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.EXACTLY_ONE
, StaticProperty.ALLOWS_ONE_OR_MORE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
public int getIntrinsicDependencies()
getIntrinsicDependencies
in class Expression
public Expression copy()
copy
in class Expression
public void explain(ExpressionPresenter destination)
explain
in class Expression
destination
- the expression presenter used to display the structure
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