|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.SimpleExpression
public abstract class SimpleExpression
An abstract implementation of Expression designed to make it easy to implement new expressions, in particular, expressions to support extension instructions.
An implementation of this class must supply the CallableExpression.call(net.sf.saxon.om.SequenceIterator[], XPathContext)
method to evaluate the expression and return its result.
Field Summary | |
---|---|
protected Expression[] |
arguments
|
static Expression[] |
NO_ARGUMENTS
|
Fields inherited from class net.sf.saxon.expr.Expression |
---|
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD |
Constructor Summary | |
---|---|
SimpleExpression()
Constructor |
Method Summary | |
---|---|
int |
computeCardinality()
Determine the static cardinality of the expression. |
int |
computeDependencies()
Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. |
Expression |
copy()
Copy an expression. |
Item |
evaluateItem(XPathContext context)
Evaluate an expression as a single item. |
void |
explain(ExpressionPresenter destination)
Diagnostic print of expression structure. |
Expression[] |
getArguments()
Get the subexpressions (arguments to this expression) |
String |
getExpressionType()
Return a distinguishing name for the expression, for use in diagnostics. |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression. |
SequenceIterator |
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence. |
Iterator<Expression> |
iterateSubExpressions()
Get the immediate sub-expressions of this expression. |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
void |
process(XPathContext context)
Process the instruction, without returning any tail calls |
Expression |
promote(PromotionOffer offer,
Expression parent)
Offer promotion for this subexpression. |
boolean |
replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression |
void |
setArguments(Expression[] sub)
Set the immediate sub-expressions of this expression. |
Expression |
simplify(ExpressionVisitor visitor)
Simplify the expression |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform type checking of an expression and its subexpressions. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Methods inherited from interface net.sf.saxon.expr.CallableExpression |
---|
call |
Field Detail |
---|
public static final Expression[] NO_ARGUMENTS
protected Expression[] arguments
Constructor Detail |
---|
public SimpleExpression()
Method Detail |
---|
public void setArguments(Expression[] sub)
sub
- an array containing the sub-expressions of this expressionpublic Iterator<Expression> iterateSubExpressions()
iterateSubExpressions
in class Expression
public boolean replaceSubExpression(Expression original, Expression replacement)
replaceSubExpression
in class Expression
original
- the original subexpressionreplacement
- the replacement subexpression
public Expression simplify(ExpressionVisitor visitor) throws XPathException
simplify
in class Expression
visitor
- an expression visitor
XPathException
- if an error is discovered during expression
rewritingpublic Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Expression
This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
If the implementation returns a value other than "this", then it is required to ensure that the location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.
typeCheck
in class 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
XPathException
- if an error is discovered during this phase
(typically a type error)public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Expression
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 class 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
XPathException
- if an error is discovered during this phase
(typically a type error)public Expression copy()
copy
in class Expression
public Expression promote(PromotionOffer offer, Expression parent) throws XPathException
promote
in class Expression
offer
- details of the offer, for example the offer to move
expressions that don't depend on the context to an outer level in
the containing expressionparent
-
XPathException
- if any error is detectedpublic ItemType getItemType(TypeHierarchy th)
getItemType
in class Expression
th
- the type hierarchy cache
public int computeCardinality()
computeCardinality
in class Expression
StaticProperty.ALLOWS_ZERO_OR_ONE
,
StaticProperty.EXACTLY_ONE
, StaticProperty.ALLOWS_ONE_OR_MORE
,
StaticProperty.ALLOWS_ZERO_OR_MORE
public int computeDependencies()
computeDependencies
in class Expression
public final Item evaluateItem(XPathContext context) throws XPathException
evaluateItem
in class Expression
context
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expressionpublic final SequenceIterator iterate(XPathContext context) throws XPathException
iterate
in class Expression
context
- supplies the context for evaluation
XPathException
- if any dynamic error occurs evaluating the
expressionpublic final void process(XPathContext context) throws XPathException
process
in class Expression
context
- The dynamic context, giving access to the current node,
the current variables, etc.
XPathException
- if a dynamic error occurspublic Expression[] getArguments()
getArguments
in interface CallableExpression
public void explain(ExpressionPresenter destination)
explain
in class Expression
destination
- the expression presenter used to display the structurepublic String getExpressionType()
|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |