Package net.sf.saxon.expr
Class PositionRange
- java.lang.Object
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- net.sf.saxon.expr.ComputedExpression
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- net.sf.saxon.expr.PositionRange
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,Container
,Expression
,InstructionInfoProvider
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)- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description (package private) boolean
maxSameAsMin
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Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
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Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors Constructor Description PositionRange(int min, int max)
Create a constant position rangePositionRange(Expression pos)
Create a position "range" for an exact positionPositionRange(Expression min, Expression max)
Create a position range
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
computeCardinality()
Determine the static cardinalityint
computeSpecialProperties()
Determine the special properties of this expressionvoid
display(int level, java.io.PrintStream out, Configuration config)
Diagnostic print of expression structureItem
evaluateItem(XPathContext c)
Evaluate the expressionint
getIntrinsicDependencies()
Get the dependenciesItemType
getItemType(TypeHierarchy th)
Determine the data type of the expressionboolean
hasFocusDependentRange()
Test whether the range is focus-dependent.boolean
isFirstPositionOnly()
Test if the first and last position are both constant 1java.util.Iterator
iterateSubExpressions()
Get the immediate sub-expressions of this expression.SequenceIterator
makePositionIterator(SequenceIterator base, XPathContext c)
Make an iterator over a range of a sequence determined by this position rangeTailExpression
makeTailExpression(Expression start)
If this is an open-ended range with a constant start position, make a TailExpression.boolean
matchesAtMostOneItem()
Test if the position range matches at most one itemExpression
optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionExpression
simplify(StaticContext env)
Simplify an expressionExpression
typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, promote, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError
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Constructor Detail
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PositionRange
public PositionRange(Expression min, Expression max)
Create a position range
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PositionRange
public PositionRange(Expression pos)
Create a position "range" for an exact position
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PositionRange
public PositionRange(int min, int max)
Create a constant position range
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Method Detail
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simplify
public Expression simplify(StaticContext env) throws XPathException
Simplify an expression- Specified by:
simplify
in interfaceExpression
- Overrides:
simplify
in classComputedExpression
- Parameters:
env
- the static context- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
Type-check the expression- Parameters:
env
- the static context of the expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
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 expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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computeSpecialProperties
public int computeSpecialProperties()
Determine the special properties of this expression- Overrides:
computeSpecialProperties
in classComputedExpression
- Returns:
StaticProperty.NON_CREATIVE
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evaluateItem
public Item evaluateItem(XPathContext c) throws XPathException
Evaluate the expression- Specified by:
evaluateItem
in interfaceExpression
- Overrides:
evaluateItem
in classComputedExpression
- Parameters:
c
- The context in which the expression is to be evaluated- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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makePositionIterator
public SequenceIterator makePositionIterator(SequenceIterator base, XPathContext c) throws XPathException
Make an iterator over a range of a sequence determined by this position range- Throws:
XPathException
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression- Parameters:
th
-- Returns:
- Type.BOOLEAN
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computeCardinality
public int computeCardinality()
Determine the static cardinality- Specified by:
computeCardinality
in classComputedExpression
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getIntrinsicDependencies
public int getIntrinsicDependencies()
Get the dependencies- Overrides:
getIntrinsicDependencies
in classComputedExpression
- Returns:
- a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
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iterateSubExpressions
public java.util.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.- Specified by:
iterateSubExpressions
in interfaceExpression
- Overrides:
iterateSubExpressions
in classComputedExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Specified by:
replaceSubExpression
in interfaceContainer
- Overrides:
replaceSubExpression
in classComputedExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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isFirstPositionOnly
public boolean isFirstPositionOnly()
Test if the first and last position are both constant 1
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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.
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matchesAtMostOneItem
public boolean matchesAtMostOneItem()
Test if the position range matches at most one item
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makeTailExpression
public TailExpression makeTailExpression(Expression start)
If this is an open-ended range with a constant start position, make a TailExpression. Otherwise return null
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display
public void display(int level, java.io.PrintStream out, Configuration config)
Diagnostic print of expression structure- Parameters:
level
- indentation level for this expressionout
- Output destination
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