net.sf.saxon.expr

Class LastItemExpression

public final class LastItemExpression extends UnaryExpression

A LastItemExpression returns the last item in the sequence returned by a given base expression. The evaluation strategy is to read the input sequence with a one-item lookahead.
Constructor Summary
LastItemExpression(Expression base)
Constructor
Method Summary
intcomputeCardinality()
Get the static cardinality
Expressioncopy()
Copy an expression.
StringdisplayExpressionName()
ItemevaluateItem(XPathContext context)
Evaluate the expression
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionpromote(PromotionOffer offer, Expression parent)
Promote this expression if possible

Constructor Detail

LastItemExpression

public LastItemExpression(Expression base)
Constructor

Parameters: base A sequence expression denoting sequence whose first item is to be returned

Method Detail

computeCardinality

public int computeCardinality()
Get the static cardinality

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

displayExpressionName

public String displayExpressionName()

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the expression

optimize

public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.

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 expresion 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: net.sf.saxon.trans.XPathException if an error is discovered during this phase (typically a type error)

promote

public Expression promote(PromotionOffer offer, Expression parent)
Promote this expression if possible