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java.lang.Object | +--net.sf.saxon.expr.ComputedExpression | +--net.sf.saxon.expr.FirstItemExpression
A FirstItemExpression returns the first item in the sequence returned by a given base expression
Field Summary |
Fields inherited from class net.sf.saxon.expr.ComputedExpression |
lineNumber, NO_ARGUMENTS, staticProperties |
Constructor Summary | |
FirstItemExpression(Expression base)
Constructor |
Method Summary | |
Expression |
analyze(StaticContext env)
Type-check the expression |
int |
computeCardinality()
Get the static cardinality |
int |
computeSpecialProperties()
Get the static properties of this expression (other than its type). |
void |
display(int level,
NamePool pool)
Diagnostic print of expression structure |
boolean |
equals(java.lang.Object other)
Is this expression the same as another expression? |
Item |
evaluateItem(XPathContext context)
Evaluate the expression |
ItemType |
getItemType()
Get the data type of the items returned |
Expression[] |
getSubExpressions()
Get the immediate subexpressions of this expression |
int |
hashCode()
get HashCode for comparing two expressions |
Expression |
promote(PromotionOffer offer)
Promote this expression if possible |
Expression |
simplify()
Simplify the expression |
Methods inherited from class net.sf.saxon.expr.ComputedExpression |
computeDependencies, computeStaticProperties, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSourceLocator, getSpecialProperties, iterate, markTailFunctionCalls, setLineNumber, typeError |
Methods inherited from class java.lang.Object |
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public FirstItemExpression(Expression base)
base
- A sequence expression denoting sequence whose first item is to be returnedMethod Detail |
public ItemType getItemType()
public Expression simplify() throws XPathException
simplify
in interface Expression
simplify
in class ComputedExpression
XPathException
- if an error is discovered during expression
rewritingpublic Expression analyze(StaticContext env) throws XPathException
env
- the static context of the expression
XPathException
public Expression promote(PromotionOffer offer) throws XPathException
promote
in interface Expression
promote
in class ComputedExpression
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 Expression[] getSubExpressions()
getSubExpressions
in interface Expression
getSubExpressions
in class ComputedExpression
public int computeCardinality()
computeCardinality
in class ComputedExpression
public boolean equals(java.lang.Object other)
equals
in class java.lang.Object
public int hashCode()
hashCode
in class java.lang.Object
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 int computeSpecialProperties()
computeSpecialProperties
in class ComputedExpression
public void display(int level, NamePool pool)
level
- indentation level for this expression
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