net.sf.saxon.expr

Class RangeExpression

public class RangeExpression extends BinaryExpression

A RangeExpression is an expression that represents an integer sequence as a pair of end-points (for example "x to y"). If the end-points are equal, the sequence is of length one.

From Saxon 7.8, the sequence must be ascending; if the end-point is less than the start-point, an empty sequence is returned. This is to allow expressions of the form "for $i in 1 to count($seq) return ...."

Constructor Summary
RangeExpression(Expression start, int op, Expression end)
Construct a RangeExpression
Method Summary
intcomputeCardinality()
Determine the static cardinality
Expressioncopy()
Copy an expression.
ItemTypegetItemType(TypeHierarchy th)
Get the data type of the items returned
SequenceIteratoriterate(XPathContext context)
Return an iteration over the sequence
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
ExpressiontypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

Constructor Detail

RangeExpression

public RangeExpression(Expression start, int op, Expression end)
Construct a RangeExpression

Parameters: start expression that computes the start of the range op represents the operator "to", needed only because this class is a subclass of BinaryExpression which needs an operator end expression that computes the end of the range

Method Detail

computeCardinality

public int computeCardinality()
Determine the static cardinality

copy

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

Returns: the copy of the original expression

getItemType

public ItemType getItemType(TypeHierarchy th)
Get the data type of the items returned

Parameters: th the type hierarchy cache

iterate

public SequenceIterator iterate(XPathContext context)
Return an iteration over the sequence

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 expression 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: XPathException if an error is discovered during this phase (typically a type error)

typeCheck

public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression