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java.lang.Objectnet.sf.saxon.expr.Expression
net.sf.saxon.expr.instruct.Instruction
net.sf.saxon.expr.instruct.Block
public class Block
An expression that delivers the concatenation of the results of its subexpressions. This may represent an XSLT sequence constructor, or an XPath/XQuery expression of the form (a,b,c,d).
| Field Summary |
|---|
| 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 | |
|---|---|
Block()
Create an empty block |
|
| Method Summary | |
|---|---|
void |
checkForUpdatingSubexpressions()
Check to ensure that this expression does not contain any updating subexpressions. |
void |
checkPermittedContents(SchemaType parentType,
StaticContext env,
boolean whole)
Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. |
int |
computeSpecialProperties()
Get the static properties of this expression (other than its type). |
Expression |
copy()
Copy an expression. |
boolean |
createsNewNodes()
Determine whether this instruction creates new nodes. |
void |
evaluatePendingUpdates(XPathContext context,
PendingUpdateList pul)
Evaluate an updating expression, adding the results to a Pending Update List. |
void |
explain(ExpressionPresenter out)
Diagnostic print of expression structure. |
int |
getCardinality()
Determine the cardinality of the expression |
Expression[] |
getChildren()
Get the children of this instruction |
String |
getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user. |
int |
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). |
ItemType |
getItemType(TypeHierarchy th)
Determine the data type of the items returned by this expression |
boolean |
isVacuousExpression()
Determine whether this is a vacuous expression as defined in the XQuery update specification |
SequenceIterator<? extends Item> |
iterate(XPathContext context)
Iterate over the results of all the child expressions |
EventIterator |
iterateEvents(XPathContext context)
Get an EventIterator over the results of all the child expressions |
Iterator<Expression> |
iterateSubExpressions()
Get the immediate sub-expressions of this expression. |
static Expression |
makeBlock(Expression e1,
Expression e2)
Static factory method to create a block. |
static Expression |
makeBlock(List<Expression> list)
Static factory method to create a block from a list of expressions |
Expression |
mergeAdjacentTextInstructions()
Merge any adjacent instructions that create literal text nodes |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
TailCall |
processLeavingTail(XPathContext context)
ProcessLeavingTail: called to do the real work of this instruction. |
protected void |
promoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites. |
boolean |
replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression |
void |
setChildren(Expression[] children)
Set the children of this instruction |
Expression |
simplify(ExpressionVisitor visitor)
Simplify an expression. |
Expression |
typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform type checking of an expression and its subexpressions. |
| Methods inherited from class net.sf.saxon.expr.instruct.Instruction |
|---|
assembleParams, assembleTunnelParams, computeCardinality, dynamicError, evaluateAsString, evaluateItem, getConstructType, getInstructionName, getInstructionNameCode, getIteratorFromProcessMethod, getSourceLocator, isXSLT, process, promote |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface javax.xml.transform.SourceLocator |
|---|
getColumnNumber, getLineNumber, getPublicId, getSystemId |
| Constructor Detail |
|---|
public Block()
| Method Detail |
|---|
public static Expression makeBlock(Expression e1,
Expression e2)
e1 - the first subexpression (child) of the blocke2 - the second subexpression (child) of the block
public static Expression makeBlock(List<Expression> list)
list - the list of expressions making up this block. The members of the List must
be instances of Expression
public void setChildren(Expression[] children)
children - The instructions that are children of this instructionpublic String getExpressionName()
Instruction
getExpressionName in class Instructionpublic Expression[] getChildren()
public int computeSpecialProperties()
Instruction
computeSpecialProperties in class Instructionpublic Expression mergeAdjacentTextInstructions()
public Iterator<Expression> iterateSubExpressions()
Expression
iterateSubExpressions in class Expression
public boolean replaceSubExpression(Expression original,
Expression replacement)
replaceSubExpression in class Expressionoriginal - the original subexpressionreplacement - the replacement subexpression
public Expression copy()
copy in class Expressionpublic final ItemType getItemType(TypeHierarchy th)
getItemType in class Instructionth - the type hierarchy cache
public final int getCardinality()
getCardinality in class Expressionpublic final boolean createsNewNodes()
createsNewNodes in class Instruction
public void checkForUpdatingSubexpressions()
throws XPathException
checkForUpdatingSubexpressions in class ExpressionXPathException - if the expression has a non-permitted updateing subexpressionpublic boolean isVacuousExpression()
isVacuousExpression in class Expression
public Expression simplify(ExpressionVisitor visitor)
throws XPathException
simplify in class Instructionvisitor - an expression visitor
XPathException - if an error is discovered during expression
rewriting
public Expression typeCheck(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
throws XPathException
ExpressionThis 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 Expressionvisitor - 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
ExpressionThis 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 Expressionvisitor - 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)
protected void promoteInst(PromotionOffer offer)
throws XPathException
promoteInst in class Instructionoffer - The type of rewrite being offered
XPathException
public void checkPermittedContents(SchemaType parentType,
StaticContext env,
boolean whole)
throws XPathException
checkPermittedContents in class ExpressionparentType - the "given complex type": the method is checking that the nodes returned by this
expression are acceptable members of the content model of this typeenv - the static contextwhole - if true, we want to check that the value of this expression satisfies the content model
as a whole; if false we want to check that the value of the expression is acceptable as one part
of the content
XPathException - if the value delivered by this expression cannot be part of the content model
of the given typepublic void explain(ExpressionPresenter out)
explain in class Expressionout - the expression presenter used to display the structure
public TailCall processLeavingTail(XPathContext context)
throws XPathException
Instruction
processLeavingTail in interface TailCallReturnerprocessLeavingTail in class Instructioncontext - The dynamic context of the transformation, giving access to the current node,
the current variables, etc.
XPathException - if a dynamic error occurs during the evaluation
of the instructionpublic int getImplementationMethod()
getImplementationMethod in class InstructionExpression.ITERATE_METHOD or Expression.EVALUATE_METHOD or
Expression.PROCESS_METHOD
public SequenceIterator<? extends Item> iterate(XPathContext context)
throws XPathException
iterate in class Instructioncontext - supplies the context for evaluation
XPathException - if any dynamic error occurs evaluating the
expression
public EventIterator iterateEvents(XPathContext context)
throws XPathException
iterateEvents in class Expressioncontext - the XPath dynamic context
XPathException - if a dynamic error occurs during expression evaluation
public void evaluatePendingUpdates(XPathContext context,
PendingUpdateList pul)
throws XPathException
evaluatePendingUpdates in class Expressioncontext - the XPath dynamic evaluation contextpul - the pending update list to which the results should be written
XPathException - if evaluation fails
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