net.sf.saxon.expr
Class SimpleMappingExpression
- ContextMappingFunction, EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator
public final class SimpleMappingExpression
A simple mapping expression is an expression A/B where B has a static type that is an atomic type.
For example, * / name().
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 |
SimpleMappingExpression
public SimpleMappingExpression(Expression start,
Expression step,
boolean isHybrid)
Constructor
start
- A node-set expression denoting the absolute or relative set of nodes from which the
navigation path should start.step
- The step to be followed from each node in the start expression to yield a new
node-setisHybrid
- if true, indicates that we don't know statically whether the step expression will
return nodes or atomic values. If false, we know it will return atomic values.
computeCardinality
public int computeCardinality()
Determine the static cardinality of the expression
- computeCardinality in interface Expression
computeDependencies
public int computeDependencies()
Determine which aspects of the context the expression depends on. The result is
a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and
XPathContext.CURRENT_NODE
- computeDependencies in interface Expression
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.
- computeSpecialProperties in interface Expression
copy
public Expression copy()
Copy an expression. This makes a deep copy.
- copy in interface Expression
- the copy of the original expression
equals
public boolean equals(Object other)
Is this expression the same as another expression?
explain
public void explain(ExpressionPresenter destination)
Diagnostic print of expression structure. The abstract expression tree
is written to the supplied output destination.
- explain in interface Expression
getStartExpression
public Expression getStartExpression()
Get the start expression (the left-hand operand)
getStepExpression
public Expression getStepExpression()
Get the step expression (the right-hand operand)
hasLoopingSubexpression
public boolean hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether
the evaluation of the parent expression causes the child expression to be
evaluated repeatedly
- hasLoopingSubexpression in interface Expression
child
- the immediate subexpression
- true if the child expression is evaluated repeatedly
hashCode
public int hashCode()
get HashCode for comparing two expressions
isHybrid
public boolean isHybrid()
Determine whether this expression is capable (as far as static analysis is concerned)
of returning a mixture of nodes and atomic values. If so, this needs to be prevented
at run time
- true if the static type allows both nodes and atomic values
iterateSubExpressions
public Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression
- iterateSubExpressions in interface Expression
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 Expression
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)
replaceSubExpression
public boolean replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression
- replaceSubExpression in interface Expression
original
- the original subexpressionreplacement
- the replacement subexpression
- true if the original subexpression is found