net.sf.saxon.expr
Class ForExpression

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.Assignation
              |
              +--net.sf.saxon.expr.ForExpression
All Implemented Interfaces:
Binding, Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

public class ForExpression
extends Assignation

A ForExpression maps an expression over a sequence. This version works with range variables, it doesn't change the context information

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.Assignation
action, declaration, nameCode, sequence, slotNumber, variableName
 
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
ForExpression()
           
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Type-check the expression
 int computeCardinality()
          Determine the static cardinality of the expression
 void display(int level, NamePool pool, java.io.PrintStream out)
          Diagnostic print of expression structure
protected  int getConstructType()
          Get the type of this expression for use in tracing and diagnostics
 ItemType getItemType()
          Determine the data type of the items returned by the expression, if possible
 SequenceIterator iterate(XPathContext context)
          Iterate over the sequence of values
 void process(XPathContext context)
          Process this expression as an instruction, writing results to the current outputter
 void setAction(Expression action)
          Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expression
 void setPositionVariable(RangeVariableDeclaration decl)
          Set the reference to the position variable (XQuery only)
 
Methods inherited from class net.sf.saxon.expr.Assignation
evaluateVariable, getVariableFingerprint, getVariableName, getVariableNameCode, iterateSubExpressions, promote, setSequence, setSlotNumber, setVariableDeclaration, simplify
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, 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
 

Constructor Detail

ForExpression

public ForExpression()
Method Detail

setPositionVariable

public void setPositionVariable(RangeVariableDeclaration decl)
Set the reference to the position variable (XQuery only)


setAction

public void setAction(Expression action)
Description copied from class: Assignation
Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expression

Overrides:
setAction in class Assignation
Parameters:
action - the expression that occurs after the "return" keyword of a "for" expression, the "satisfies" keyword of "some/every", or the ":=" operator of a "let" expression.

This method must be called after calling setVariableDeclaration()


analyze

public Expression analyze(StaticContext env,
                          ItemType contextItemType)
                   throws XPathException
Type-check the expression

Parameters:
env - the static context of the expression
contextItemType - 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
Returns:
the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
XPathException

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Iterate over the sequence of values

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
Parameters:
context - supplies the context for evaluation
Returns:
a SequenceIterator that can be used to iterate over the result of the expression
Throws:
XPathException - if any dynamic error occurs evaluating the expression

process

public void process(XPathContext context)
             throws XPathException
Process this expression as an instruction, writing results to the current outputter

Specified by:
process in interface Expression
Overrides:
process in class ComputedExpression
Parameters:
context - The dynamic context, giving access to the current node, the current variables, etc.
XPathException

getItemType

public ItemType getItemType()
Determine the data type of the items returned by the expression, if possible

Returns:
one of the values Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)

computeCardinality

public int computeCardinality()
Determine the static cardinality of the expression

Specified by:
computeCardinality in class ComputedExpression

display

public void display(int level,
                    NamePool pool,
                    java.io.PrintStream out)
Diagnostic print of expression structure

Parameters:
level - indentation level for this expression
pool - NamePool used to expand any names appearing in the expression
out - Output destination

getConstructType

protected int getConstructType()
Get the type of this expression for use in tracing and diagnostics

Overrides:
getConstructType in class ComputedExpression
Returns:
the type of expression, as enumerated in class Location