net.sf.saxon.sort

Class TupleExpression

public class TupleExpression extends ComputedExpression

A tuple expression is an expression that returns a tuple. Specifically, it is a list of n expressions, which are evaluated to create a list of n items. Tuple expressions are used during the evaluation of a FLWR expression. A tuple is not a value within the XPath/XQuery type system, so it is represented as an external object, specifically as a Java array wrapped inside an ObjectValue.
Field Summary
Expression[]components
Constructor Summary
TupleExpression(int width)
Method Summary
intcomputeCardinality()
Get the cardinality of the expression.
voiddisplay(int level, NamePool pool, PrintStream out)
ItemevaluateItem(XPathContext context)
intgetIntrinsicDependencies()
ItemTypegetItemType(TypeHierarchy th)
IteratoriterateSubExpressions()
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionpromote(PromotionOffer offer)
voidsetExpression(int i, Expression exp)
Expressionsimplify(StaticContext env)
ExpressiontypeCheck(StaticContext env, ItemType contextItemType)

Field Detail

components

Expression[] components

Constructor Detail

TupleExpression

public TupleExpression(int width)

Method Detail

computeCardinality

public int computeCardinality()
Get the cardinality of the expression. This is exactly one, in the sense that evaluating the TupleExpression returns a single tuple.

Returns: the static cardinality - EXACTLY_ONE

display

public void display(int level, NamePool pool, PrintStream out)

evaluateItem

public Item evaluateItem(XPathContext context)

getIntrinsicDependencies

public int getIntrinsicDependencies()

getItemType

public ItemType getItemType(TypeHierarchy th)

iterateSubExpressions

public Iterator iterateSubExpressions()

optimize

public Expression optimize(Optimizer opt, StaticContext env, 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: opt the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances. env the static context of the expression 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.StaticError if an error is discovered during this phase (typically a type error)

promote

public Expression promote(PromotionOffer offer)

setExpression

public void setExpression(int i, Expression exp)

simplify

public Expression simplify(StaticContext env)

typeCheck

public Expression typeCheck(StaticContext env, ItemType contextItemType)