net.sf.saxon.expr
Class SingletonAtomizer
- EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator
public final class SingletonAtomizer
A SingletonAtomizer combines the functions of an Atomizer and a CardinalityChecker: it is used to
atomize a sequence of nodes, checking that the result of the atomization contains zero or one atomic
values. Note that the input may be a sequence of nodes or atomic values, even though the result must
contain at most one atomic value.
computeCardinality , computeSpecialProperties , displayExpressionName , displayOperator , equals , explain , getBaseExpression , getItemType , hashCode , iterateSubExpressions , optimize , promote , replaceSubExpression , simplify , toString , typeCheck |
addToPathMap , adoptChildExpression , checkPermittedContents , computeCardinality , computeDependencies , computeSpecialProperties , computeStaticProperties , copy , display , doPromotion , dynamicError , effectiveBooleanValue , evaluateAsString , evaluateItem , explain , explain , findParentOf , getCardinality , getColumnNumber , getConstructType , getContainer , getDependencies , getExecutable , getHostLanguage , getImplementationMethod , getInstructionInfo , getIntrinsicDependencies , getItemType , getLineNumber , getLocationId , getLocationProvider , getPublicId , getSlotsUsed , getSpecialProperties , getSystemId , hasLoopingSubexpression , implementsStaticTypeCheck , iterate , iterateEvents , iterateSubExpressions , markTailFunctionCalls , optimize , process , promote , replaceSubExpression , resetLocalStaticProperties , setContainer , setFiltered , setFlattened , setLocationId , simplify , staticTypeCheck , suppressValidation , toString , typeCheck , typeError |
SingletonAtomizer
public SingletonAtomizer(Expression sequence,
RoleLocator role,
boolean allowEmpty)
Constructor
sequence
- the sequence to be atomizedrole
- contains information about where the expression appears, for use in any error messageallowEmpty
- true if the result sequence is allowed to be empty.
addToPathMap
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited
by an expression in a source tree.
The default implementation of this method assumes that an expression does no navigation other than
the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the
same context as the containing expression. The method must be overridden for any expression
where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression,
and RootExpression (because they perform navigation), and for the doc(), document(), and collection()
functions because they create a new navigation root. Implementations also exist for PathExpression and
FilterExpression because they have subexpressions that are evaluated in a different context from the
calling expression.
- addToPathMap in interface Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
- the PathMapNodeSet to which the paths embodied in this expression should be added
- the pathMapNodeSet representing the points in the source document that are both reachable by this
expression, and that represent possible results of this expression. For an expression that does
navigation, it represents the end of the arc in the path map that describes the navigation route. For other
expressions, it is the same as the input pathMapNode.
copy
public Expression copy()
Copy an expression. This makes a deep copy.
- copy in interface Expression
- the copy of the original expression
displayExpressionName
protected String displayExpressionName()
Give a string representation of the expression name for use in diagnostics
- displayExpressionName in interface UnaryExpression
- the expression name, as a string
getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible
- getItemType in interface UnaryExpression
th
- the type hierarchy cache
- a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the
result is always an atomic type, but it might be more specific.
getRole
public RoleLocator getRole()
Get the RoleLocator (used to construct error messages)
optimize
public Expression optimize(ExpressionVisitor visitor,
ItemType contextItemType)
throws XPathException
Perform optimisation of an expression and its subexpressions. This is the third and final
phase of static optimization.
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.
- optimize in interface UnaryExpression
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 to
Type.ITEM_TYPE
- the original expression, rewritten if appropriate to optimize execution
XPathException
- if an error is discovered during this phase
(typically a type error)