RpEval (Java Expression Parser 2.4.2 API)

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

All Implemented Interfaces:

ParserVisitor
```
public final class RpEval
extends 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

Fields
Modifier and Type	Field and Description
`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

Constructors
Constructor and Description

RpEval(JEP jep)

Constructors
Constructor and Description
`RpEval(JEP jep)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`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.
`String`	`getFunction(short ref)`
`Variable`	`getVariable(int ref)`
`Object`	`visit(ASTConstant node, Object data)`
`Object`	`visit(ASTFunNode node, Object data)`
`Object`	`visit(ASTStart node, Object data)`
`Object`	`visit(ASTVarNode node, Object data)`
`Object`	`visit(SimpleNode node, 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 Object visit(ASTStart node,
                          Object data)
                   throws ParseException

Specified by:: visit in interface ParserVisitor
Throws:: ParseException

visit

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

Specified by:: visit in interface ParserVisitor
Throws:: ParseException

visit

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

Specified by:: visit in interface ParserVisitor
Throws:: ParseException

visit

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

Specified by:: visit in interface ParserVisitor
Throws:: ParseException

visit

public final Object visit(ASTFunNode node,
                          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 String getFunction(short ref)
```

Class RpEval

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

CONST

VAR

ADD

SUB

MUL

DIV

MOD

POW

AND

OR

NOT

LT

LE

GT

GE

NE

EQ

LIST

DOT

CROSS

ASSIGN

VLIST

MLIST

FUN

UMINUS

Constructor Detail

RpEval

Method Detail

compile

visit

visit

visit

visit

visit

evaluate

cleanUp

getVariable

getFunction