com.icl.saxon.expr
Class RelationalExpression

java.lang.Object
  |
  +--com.icl.saxon.expr.Expression
        |
        +--com.icl.saxon.expr.BinaryExpression
              |
              +--com.icl.saxon.expr.RelationalExpression

final class RelationalExpression

extends BinaryExpression

Relational Expression: a boolean expression that compares two expressions for equals, not-equals, greater-than or less-than.

Field Summary

protected int	operator
protected Expression	p1
protected Expression	p2

Fields inherited from class com.icl.saxon.expr.Expression

staticContext

Constructor Summary

RelationalExpression()
Default constructor

RelationalExpression(Expression p1, int op, Expression p2)
Create a relational expression identifying the two operands and the operator

Method Summary

void	display(int level) Diagnostic print of expression structure
Value	evaluate(Context c) Evaluate the expression in a given context
boolean	evaluateAsBoolean(Context c) Evaluate the expression in a given context
int	getDataType() Determine the data type of the expression
int	getDependencies() Determine which aspects of the context the expression depends on.
Expression	reduce(int dependencies, Context context) Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
void	setDetails(Expression p1, int op, Expression p2) Identify the two operands and the operator (for use when the default constructor was used)
Expression	simplify() Simplify an expression

Methods inherited from class com.icl.saxon.expr.Expression

containsReferences, enumerate, evaluateAsNodeSet, evaluateAsNumber, evaluateAsString, getStaticContext, indent, isContextDocumentNodeSet, make, outputStringValue, setStaticContext, usesCurrent

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

p1

protected Expression p1

p2

protected Expression p2

operator

protected int operator

Constructor Detail

RelationalExpression

public RelationalExpression()

Default constructor

RelationalExpression

public RelationalExpression(Expression p1,
                            int op,
                            Expression p2)

Create a relational expression identifying the two operands and the operator

Parameters:

p1 - the left-hand operand

op - the operator, as a token returned by the Tokenizer (e.g. Tokenizer.LT)

p2 - the right-hand operand

Method Detail

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Overrides:

simplify in class BinaryExpression

Returns:

the simplified expression

XPathException

evaluate

public Value evaluate(Context c)
               throws XPathException

Evaluate the expression in a given context

Specified by:

evaluate in class Expression

Parameters:

c - the given context for evaluation

Returns:

a BooleanValue representing the result of the numeric comparison of the two operands

XPathException

evaluateAsBoolean

public boolean evaluateAsBoolean(Context c)
                          throws XPathException

Evaluate the expression in a given context

Overrides:

evaluateAsBoolean in class Expression

Parameters:

c - the given context for evaluation

Returns:

a boolean representing the result of the numeric comparison of the two operands

XPathException

getDataType

public int getDataType()

Determine the data type of the expression

Specified by:

getDataType in class Expression

Returns:

Value.BOOLEAN

reduce

public Expression reduce(int dependencies,
                         Context context)
                  throws XPathException

Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.

Specified by:

reduce in class Expression

Parameters:

dependencies - The dependencies to be removed

context - The context to be used for the partial evaluation

Returns:

a new expression that does not have any of the specified dependencies

XPathException

setDetails

public void setDetails(Expression p1,
                       int op,
                       Expression p2)

Identify the two operands and the operator (for use when the default constructor was used)

Parameters:

p1 - the left-hand operand

op - the operator, as a token returned by the Tokenizer (e.g. Tokenizer.AND)

p2 - the right-hand operand

getDependencies

public int getDependencies()

Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as Context.VARIABLES and Context.CURRENT_NODE

Specified by:

getDependencies in class Expression

display

public void display(int level)

Diagnostic print of expression structure

Specified by:

display in class Expression