org.lsmp.djep.djep

Class DifferentiationVisitor

java.lang.Object

org.lsmp.djep.xjep.DoNothingVisitor

org.lsmp.djep.xjep.DeepCopyVisitor

org.lsmp.djep.djep.DifferentiationVisitor

All Implemented Interfaces:

ParserVisitor

public class DifferentiationVisitor
extends DeepCopyVisitor

A class for performing differentation of an expression. To use do

 JEP j = ...; Node in = ...;
 DifferentiationVisitor dv = new DifferentiationVisitor(jep);
 dv.addStandardDiffRules();
 Node out = dv.differentiate(in,"x");
 

The class follows the visitor pattern described in ParserVisitor. The rules for differentiating specific functions are contained in object which implement DiffRulesI A number of inner classes which use this interface are defined for specific function types. In particular MacroDiffRules allow the rule for differentiation to be specified by strings. New rules can be added using DJep.addDiffRule(org.lsmp.djep.djep.DiffRulesI) method.

Author:

R Morris Created on 19-Jun-2003

Constructor Summary

Constructors

Constructor and Description
DifferentiationVisitor(DJep jep) Construction with a given set of tree utilities

Method Summary

Modifier and Type	Method and Description
Node	differentiate(Node node, String var, DJep djep) Differentiates an expression tree wrt a variable var.
boolean	isConstantVar(XVariable var)
void	printDiffRules() Prints all the differentation rules for all functions on System.out.
void	printDiffRules(PrintStream out) Prints all the differentation rules for all functions on specified stream.
Object	visit(ASTConstant node, Object data) Differentiates a constant.
Object	visit(ASTFunNode node, Object data) Applies differentiation to a function.
Object	visit(ASTVarNode node, Object data) Differentiates a variable.

Methods inherited from class org.lsmp.djep.xjep.DeepCopyVisitor

deepCopy

Methods inherited from class org.lsmp.djep.xjep.DoNothingVisitor

acceptChildrenAsArray, visit, visit

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.nfunk.jep.ParserVisitor

visit, visit

Constructor Detail

DifferentiationVisitor

public DifferentiationVisitor(DJep jep)

Construction with a given set of tree utilities

Method Detail

printDiffRules

public void printDiffRules()

Prints all the differentation rules for all functions on System.out.

printDiffRules

public void printDiffRules(PrintStream out)

Prints all the differentation rules for all functions on specified stream.

differentiate

public Node differentiate(Node node,
                          String var,
                          DJep djep)
                   throws ParseException,
                          IllegalArgumentException

Differentiates an expression tree wrt a variable var.

Parameters:

node - the top node of the expression tree

var - the variable to differentiate wrt

Returns:

the top node of the differentiated expression

Throws:

ParseException - if some error occurred while trying to differentiate, for instance of no rule supplied for given function.

IllegalArgumentException

visit

public Object visit(ASTFunNode node,
                    Object data)
             throws ParseException

Applies differentiation to a function. Used the rules specified by objects of type DiffRulesI.

Specified by:

visit in interface ParserVisitor

Overrides:

visit in class DeepCopyVisitor

Parameters:

node - The node of the function.

data - The variable to differentiate wrt.

Throws:

ParseException

isConstantVar

public boolean isConstantVar(XVariable var)

visit

public Object visit(ASTVarNode node,
                    Object data)
             throws ParseException

Differentiates a variable. May want to alter behaviour when using multi equation as diff(f,x) might not be zero.

Specified by:

visit in interface ParserVisitor

Overrides:

visit in class DeepCopyVisitor

Returns:

1 if the variable has the same name as data, 0 if the variable has a different name.

Throws:

ParseException

visit

public Object visit(ASTConstant node,
                    Object data)
             throws ParseException

Differentiates a constant.

Specified by:

visit in interface ParserVisitor

Overrides:

visit in class DeepCopyVisitor

Returns:

0 derivatives of constants are always zero.

Throws:

ParseException