| java.lang.Object
 net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.FirstItemExpression
| FirstItemExpression | | final public class FirstItemExpression extends UnaryExpression (Code) | | A FirstItemExpression returns the first item in the sequence returned by a given
base expression
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| FirstItemExpression | | public FirstItemExpression(Expression base)(Code) | | Constructor
Parameters:
base - A sequence expression denoting sequence whose first item is to be returned |
| computeCardinality | | public int computeCardinality()(Code) | | Get the static cardinality
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| displayOperator | | public String displayOperator(NamePool pool)(Code) | | Diagnostic print of expression structure
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| optimize | | public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException(Code) | | 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:
opt - the optimizer in use. This provides access to supporting functions; it also allowsdifferent optimization strategies to be used in different circumstances.
Parameters:
env - the static context of the expression
Parameters:
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 tonet.sf.saxon.type.Type.ITEM_TYPE the original expression, rewritten if appropriate to optimize execution
throws:
net.sf.saxon.trans.StaticError - if an error is discovered during this phase(typically a type error) |
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