net.sf.saxon.expr

Class PositionRange

public final class PositionRange extends ComputedExpression

PositionRange: a boolean expression that tests whether the position() is within a certain range. This expression can occur in any context but it is optimized when it appears as a predicate (see FilterIterator)
Constructor Summary
PositionRange(Expression min, Expression max)
Create a position range
PositionRange(int min, int max)
Create a constant position range
Method Summary
intcomputeCardinality()
Determine the static cardinality
intcomputeSpecialProperties()
Determine the special properties of this expression
voiddisplay(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure
ItemevaluateItem(XPathContext c)
Evaluate the expression
intgetIntrinsicDependencies()
Get the dependencies
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression
booleanhasFocusDependentRange()
Test whether the range is focus-dependent.
booleanisFirstPositionOnly()
Test if the first and last position are both constant 1
IteratoriterateSubExpressions()
Get the immediate sub-expressions of this expression.
SequenceIteratormakePositionIterator(SequenceIterator base, XPathContext c)
Make an iterator over a range of a sequence determined by this position range
TailExpressionmakeTailExpression(Expression start)
If this is an open-ended range with a constant start position, make a TailExpression.
booleanmatchesAtMostOneItem()
Test if the position range matches at most one item
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionsimplify(StaticContext env)
Simplify an expression
ExpressiontypeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression

Constructor Detail

PositionRange

public PositionRange(Expression min, Expression max)
Create a position range

PositionRange

public PositionRange(int min, int max)
Create a constant position range

Method Detail

computeCardinality

public int computeCardinality()
Determine the static cardinality

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression

Returns: NON_CREATIVE.

display

public void display(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure

evaluateItem

public Item evaluateItem(XPathContext c)
Evaluate the expression

getIntrinsicDependencies

public int getIntrinsicDependencies()
Get the dependencies

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression

Parameters: th

Returns: Type.BOOLEAN

hasFocusDependentRange

public boolean hasFocusDependentRange()
Test whether the range is focus-dependent. An example of a focus-dependent range is (1 to position()). We could treat last() specially but we don't.

isFirstPositionOnly

public boolean isFirstPositionOnly()
Test if the first and last position are both constant 1

iterateSubExpressions

public Iterator iterateSubExpressions()
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Returns: an iterator containing the sub-expressions of this expression

makePositionIterator

public SequenceIterator makePositionIterator(SequenceIterator base, XPathContext c)
Make an iterator over a range of a sequence determined by this position range

makeTailExpression

public TailExpression makeTailExpression(Expression start)
If this is an open-ended range with a constant start position, make a TailExpression. Otherwise return null

matchesAtMostOneItem

public boolean matchesAtMostOneItem()
Test if the position range matches at most one item

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)

simplify

public Expression simplify(StaticContext env)
Simplify an expression

Returns: the simplified expression

typeCheck

public Expression typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression