Package net.sf.saxon.expr
Class CardinalityChecker
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.CardinalityChecker
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,InstructionInfo
,Locator
A CardinalityChecker implements the cardinality checking of "treat as": that is,
it returns the supplied sequence, checking that its cardinality is correct
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Method Summary
Modifier and TypeMethodDescriptionint
Determine the static cardinality of the expressionint
Get the static properties of this expression (other than its type).copy()
Copy an expression.static String
depictSequenceStart
(SequenceIterator seq, int max) Show the first couple of items in a sequence in an error messageboolean
Is this expression the same as another expression?evaluateItem
(XPathContext context) Evaluate as an Item.void
Diagnostic print of expression structure.int
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().Determine the data type of the items returned by the expression, if possibleint
Get the required cardinalityGet the RoleLocator, which contains diagnostic information for use if the cardinality check failsiterate
(XPathContext context) Iterate over the sequence of valuesstatic Expression
makeCardinalityChecker
(Expression sequence, int cardinality, RoleLocator role) Factory method to construct a CardinalityChecker.optimize
(ExpressionVisitor visitor, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.void
process
(XPathContext context) Process the instruction, without returning any tail callsvoid
setErrorCode
(String code) Set the error code to be returned (this is used when evaluating the functions such as exactly-one() which have their own error codes)typeCheck
(ExpressionVisitor visitor, ItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.UnaryExpression
displayExpressionName, displayOperator, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression, simplify, toString
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Method Details
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makeCardinalityChecker
public static Expression makeCardinalityChecker(Expression sequence, int cardinality, RoleLocator role) Factory method to construct a CardinalityChecker. The method may create an expression that combines the cardinality checking with the functionality of the underlying expression class- Parameters:
sequence
- the base sequence whose cardinality is to be checkedcardinality
- the required cardinalityrole
- information to be used in error reporting- Returns:
- a new Expression that does the CardinalityChecking (not necessarily a CardinalityChecker)
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getRequiredCardinality
public int getRequiredCardinality()Get the required cardinality- Returns:
- the cardinality required by this checker
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException Type-check the expression- Overrides:
typeCheck
in classUnaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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:
XPathException
- if an error is discovered during this phase (typically a type error)
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optimize
public Expression optimize(ExpressionVisitor visitor, 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.
- Overrides:
optimize
in classUnaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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:
XPathException
- if an error is discovered during this phase (typically a type error)
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setErrorCode
Set the error code to be returned (this is used when evaluating the functions such as exactly-one() which have their own error codes)- Parameters:
code
- the error code to be used
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getRoleLocator
Get the RoleLocator, which contains diagnostic information for use if the cardinality check fails- Returns:
- the diagnostic information
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getImplementationMethod
public int getImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided. This implementation provides both iterate() and process() methods natively.- Overrides:
getImplementationMethod
in classExpression
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
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iterate
Iterate over the sequence of values- Specified by:
iterate
in interfaceSequenceIterable
- Overrides:
iterate
in classExpression
- Parameters:
context
- supplies the context for evaluation- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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depictSequenceStart
Show the first couple of items in a sequence in an error message- Parameters:
seq
- iterator over the sequencemax
- maximum number of items to be shown- Returns:
- a message display of the contents of the sequence
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evaluateItem
Evaluate as an Item.- Specified by:
evaluateItem
in interfaceEvaluableItem
- Overrides:
evaluateItem
in classExpression
- Parameters:
context
- 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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process
Process the instruction, without returning any tail calls- Overrides:
process
in classExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
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getItemType
Determine the data type of the items returned by the expression, if possible- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
- the type hierarchy cache- Returns:
- a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
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computeCardinality
public int computeCardinality()Determine the static cardinality of the expression- Overrides:
computeCardinality
in classUnaryExpression
- Returns:
- the computed cardinality, as one of the values
StaticProperty.ALLOWS_ZERO_OR_ONE
,StaticProperty.EXACTLY_ONE
,StaticProperty.ALLOWS_ONE_OR_MORE
,StaticProperty.ALLOWS_ZERO_OR_MORE
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computeSpecialProperties
public int computeSpecialProperties()Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.- Overrides:
computeSpecialProperties
in classUnaryExpression
- Returns:
- the special properties, as a bit-significant integer
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copy
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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equals
Is this expression the same as another expression?- Overrides:
equals
in classUnaryExpression
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explain
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Overrides:
explain
in classUnaryExpression
- Parameters:
out
- the expression presenter used to display the structure
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