net.sf.saxon.expr
Class AppendExpression

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

public final class AppendExpression
extends net.sf.saxon.expr.BinaryExpression

An expression representing a sequence that is the concatenation of two given sequences. This implements the "comma" operator in XPath sequence expressions.

See Also:
Serialized Form

Nested Class Summary
static class AppendExpression.AppendIterator
          Iterator that concatenates the results of two supplied iterators
 
Field Summary
protected  Expression operand0
           
protected  Expression operand1
           
protected  int operator
           
 
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
AppendExpression(Expression p1, int op, Expression p2)
          Constructor
 
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  java.lang.String displayOperator()
           
 boolean equals(java.lang.Object other)
          Is this expression the same as another expression?
 ItemType getItemType()
          Determine the data type of the items returned by this expression
 int hashCode()
          get HashCode for comparing two expressions.
protected static boolean isCommutative(int operator)
           
 SequenceIterator iterate(XPathContext c)
          Iterate over the value of the expression.
 java.util.Iterator iterateSubExpressions()
          Get the immediate subexpressions of this expression
 Expression promote(PromotionOffer offer)
          Promote this expression if possible
 Expression simplify(StaticContext env)
          Simplify the expression
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

operand0

protected Expression operand0

operand1

protected Expression operand1

operator

protected int operator
Constructor Detail

AppendExpression

public AppendExpression(Expression p1,
                        int op,
                        Expression p2)
Constructor

Parameters:
p1 - the left-hand operand
op - the operator (always ",")
p2 - the right-hand operand
Method Detail

getItemType

public final ItemType getItemType()
Determine the data type of the items returned by this expression

Returns:
the data type

computeCardinality

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

Overrides:
computeCardinality in class net.sf.saxon.expr.BinaryExpression

simplify

public Expression simplify(StaticContext env)
                    throws XPathException
Simplify the expression

Specified by:
simplify in interface Expression
Overrides:
simplify in class net.sf.saxon.expr.BinaryExpression
Returns:
the simplified expression
XPathException

iterate

public SequenceIterator iterate(XPathContext c)
                         throws XPathException
Iterate over the value of the expression.

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
Parameters:
c - The context for evaluation
Returns:
a SequenceIterator representing the concatenation of the two operands
Throws:
XPathException - if any dynamic error occurs evaluating the expression

analyze

public Expression analyze(StaticContext env,
                          ItemType contextItemType)
                   throws XPathException
Type-check the expression. Default implementation for binary operators that accept any kind of operand

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

promote

public Expression promote(PromotionOffer offer)
                   throws XPathException
Promote this expression if possible

Specified by:
promote in interface Expression
Overrides:
promote in class ComputedExpression
Parameters:
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 expression
Returns:
if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
Throws:
XPathException - if any error is detected

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression

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

isCommutative

protected static boolean isCommutative(int operator)

equals

public boolean equals(java.lang.Object other)
Is this expression the same as another expression?

Overrides:
equals in class java.lang.Object

hashCode

public int hashCode()
get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

Overrides:
hashCode in class java.lang.Object

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

displayOperator

protected java.lang.String displayOperator()