net.sf.saxon.instruct
Class InstructionWithChildren

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.instruct.Instruction
              |
              +--net.sf.saxon.instruct.InstructionWithChildren
All Implemented Interfaces:
Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator
Direct Known Subclasses:
Block, Doctype, DocumentInstr, ElementCreator, Message, ResultDocument, SimpleNodeConstructor

public abstract class InstructionWithChildren
extends Instruction

Abstract superclass for all instructions in the compiled stylesheet that have child instructions. This does not include instructions such as xsl:perform-sort that have child instructions, but whose child instructions are compiled directly into an expression (or a Block).

See Also:
Serialized Form

Field Summary
protected  Expression[] children
           
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
InstructionWithChildren()
          Constructor
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Perform static analysis of an expression and its subexpressions.
static void displayChildren(Expression[] children, int level, NamePool pool, java.io.PrintStream out)
          Display the children of an instruction for diagostics
 Expression[] getChildren()
          Get the children of this instruction
 java.util.Iterator iterateSubExpressions()
          Get the immediate sub-expressions of this expression.
protected  void processChildren(XPathContext context)
          Process the children of this instruction, including any tail calls
protected  TailCall processChildrenLeavingTail(XPathContext context)
          Process the children of this instruction, returning any tail call made by the last child instruction
protected  void promoteInst(PromotionOffer offer)
          Handle promotion offers, that is, non-local tree rewrites.
 void setChildren(Expression[] children)
          Set the children of this instruction
 Expression simplify(StaticContext env)
          Simplify an expression.
 
Methods inherited from class net.sf.saxon.instruct.Instruction
appendItem, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, iterate, process, processLeavingTail, promote
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeStaticProperties, dynamicError, dynamicError, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface javax.xml.transform.SourceLocator
getColumnNumber, getLineNumber, getPublicId, getSystemId
 
Methods inherited from interface net.sf.saxon.expr.Expression
display
 

Field Detail

children

protected Expression[] children
Constructor Detail

InstructionWithChildren

public InstructionWithChildren()
Constructor

Method Detail

setChildren

public void setChildren(Expression[] children)
Set the children of this instruction

Parameters:
children - The instructions that are children of this instruction

getChildren

public Expression[] getChildren()
Get the children of this instruction

Returns:
the children of this instruction, as an array of Instruction objects. May return either a zero-length array or null if there are no children

displayChildren

public static void displayChildren(Expression[] children,
                                   int level,
                                   NamePool pool,
                                   java.io.PrintStream out)
Display the children of an instruction for diagostics


simplify

public Expression simplify(StaticContext env)
                    throws XPathException
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).

Specified by:
simplify in interface Expression
Specified by:
simplify in class Instruction
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

analyze

public Expression analyze(StaticContext env,
                          ItemType contextItemType)
                   throws XPathException
Perform static analysis of an expression and its subexpressions.

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 will only be accurately known if they have been explicitly declared.

Specified by:
analyze in interface Expression
Specified by:
analyze in class Instruction
Parameters:
env - the static context of the expression
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)

promoteInst

protected void promoteInst(PromotionOffer offer)
                    throws XPathException
Handle promotion offers, that is, non-local tree rewrites.

Overrides:
promoteInst in class Instruction
Parameters:
offer - The type of rewrite being offered
Throws:
XPathException

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()
Get the immediate sub-expressions of this expression.

Specified by:
iterateSubExpressions in interface Expression
Overrides:
iterateSubExpressions in class ComputedExpression
Returns:
an iterator containing the sub-expressions of this expression

processChildren

protected void processChildren(XPathContext context)
                        throws XPathException
Process the children of this instruction, including any tail calls

Parameters:
context - The dynamic context for the transformation
Throws:
XPathException - if a dynamic error occurs

processChildrenLeavingTail

protected TailCall processChildrenLeavingTail(XPathContext context)
                                       throws XPathException
Process the children of this instruction, returning any tail call made by the last child instruction

Parameters:
context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.
Returns:
null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
XPathException