org.lsmp.djep.rpe
Class RpEval

java.lang.Object
  org.lsmp.djep.rpe.RpEval

All Implemented Interfaces:

ParserVisitor

public final class RpEval
extends java.lang.Object
implements ParserVisitor

A fast evaluation algorithm for equations over Doubles, does not work with vectors or matricies. This is based around reverse polish notation and is optimised for speed at every opportunity.

To use do

 JEP j = ...;
 Node node = ...; 
 RpEval rpe = new RpEval(j);
 RpCommandList list = rpe.compile(node);
 double val = rpe.evaluate(list);
 System.out.println(val);
 rpe.cleanUp();
 

The compile methods converts the expression represented by node into a string of commands. For example the expression "1+2*3" will be converted into the sequence of commands

 Constant no 1 (pushes constant onto stack)
 Constant no 2
 Constant no 3
 Multiply scalers (multiplies last two entries on stack)
 Add scalers (adds last two entries on stack)
 

The evaluate method executes these methods sequentially using a stack and returns the last object on the stack.

A few cautionary notes: Its very unlikely to be thread safe. It only works over doubles expressions with complex numbers or strings will cause problems. It only works for expressions involving scalers.

Implementation notes A lot of things have been done to make it as fast as possible:

• Everything is final which maximises the possibility for in-lining.
• All object creation happens during compile.
• All calculations done using double values.
• Each operator/function is hand coded. To extend functionality you will have to modify the source.

Author:

Rich Morris Created on 14-Apr-2004

Field Summary

static short	ADD
static short	AND
static short	ASSIGN
static short	CONST Index for each command
static short	CROSS
static short	DIV
static short	DOT
static short	EQ
static short	FUN
static short	GE
static short	GT
static short	LE
static short	LIST
static short	LT
static short	MLIST
static short	MOD
static short	MUL
static short	NE
static short	NOT
static short	OR
static short	POW
static short	SUB
static short	UMINUS
static short	VAR
static short	VLIST

Constructor Summary

RpEval(JEP jep)

Method Summary

void	cleanUp() Removes observers and other cleanup needed when evaluator no longer used.
RpCommandList	compile(Node node) Compile the expressions to produce a set of commands in reverse Polish notation.
double	evaluate(RpCommandList comList) Evaluate the expression.
java.lang.String	getFunction(short ref)
Variable	getVariable(int ref)
java.lang.Object	visit(ASTConstant node, java.lang.Object data)
java.lang.Object	visit(ASTFunNode node, java.lang.Object data)
java.lang.Object	visit(ASTStart node, java.lang.Object data)
java.lang.Object	visit(ASTVarNode node, java.lang.Object data)
java.lang.Object	visit(SimpleNode node, java.lang.Object data)

Methods inherited from class java.lang.Object

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

Field Detail

CONST

public static final short CONST

Index for each command

See Also:

Constant Field Values

VAR

public static final short VAR

See Also:

Constant Field Values

ADD

public static final short ADD

See Also:

Constant Field Values

SUB

public static final short SUB

See Also:

Constant Field Values

MUL

public static final short MUL

See Also:

Constant Field Values

DIV

public static final short DIV

See Also:

Constant Field Values

MOD

public static final short MOD

See Also:

Constant Field Values

POW

public static final short POW

See Also:

Constant Field Values

AND

public static final short AND

See Also:

Constant Field Values

OR

public static final short OR

See Also:

Constant Field Values

NOT

public static final short NOT

See Also:

Constant Field Values

LT

public static final short LT

See Also:

Constant Field Values

LE

public static final short LE

See Also:

Constant Field Values

GT

public static final short GT

See Also:

Constant Field Values

GE

public static final short GE

See Also:

Constant Field Values

NE

public static final short NE

See Also:

Constant Field Values

EQ

public static final short EQ

See Also:

Constant Field Values

LIST

public static final short LIST

See Also:

Constant Field Values

DOT

public static final short DOT

See Also:

Constant Field Values

CROSS

public static final short CROSS

See Also:

Constant Field Values

ASSIGN

public static final short ASSIGN

See Also:

Constant Field Values

VLIST

public static final short VLIST

See Also:

Constant Field Values

MLIST

public static final short MLIST

See Also:

Constant Field Values

FUN

public static final short FUN

See Also:

Constant Field Values

UMINUS

public static final short UMINUS

See Also:

Constant Field Values

Constructor Detail

RpEval

public RpEval(JEP jep)

Method Detail

compile

public final RpCommandList compile(Node node)
                            throws ParseException

Compile the expressions to produce a set of commands in reverse Polish notation.

Throws:

ParseException

visit

public final java.lang.Object visit(ASTStart node,
                                    java.lang.Object data)
                             throws ParseException

Specified by:

visit in interface ParserVisitor

Throws:

ParseException

visit

public final java.lang.Object visit(SimpleNode node,
                                    java.lang.Object data)
                             throws ParseException

Specified by:

visit in interface ParserVisitor

Throws:

ParseException

visit

public final java.lang.Object visit(ASTConstant node,
                                    java.lang.Object data)
                             throws ParseException

Specified by:

visit in interface ParserVisitor

Throws:

ParseException

visit

public final java.lang.Object visit(ASTVarNode node,
                                    java.lang.Object data)
                             throws ParseException

Specified by:

visit in interface ParserVisitor

Throws:

ParseException

visit

public final java.lang.Object visit(ASTFunNode node,
                                    java.lang.Object data)
                             throws ParseException

Specified by:

visit in interface ParserVisitor

Throws:

ParseException

evaluate

public final double evaluate(RpCommandList comList)

Evaluate the expression.

Returns:

the double value of the equation

cleanUp

public void cleanUp()

Removes observers and other cleanup needed when evaluator no longer used.

getVariable

public Variable getVariable(int ref)

getFunction

public java.lang.String getFunction(short ref)