JELFunction (Starjava TTOOLS API)

java.lang.Object
- uk.ac.starlink.ttools.jel.JELFunction

```
public class JELFunction
extends java.lang.Object
```
Provides a double precision function of one double precision variable which can be evaluated using JEL. The variable name and an expression giving the result in terms of that variable name are supplied.
Instances of this class are not threadsafe, but could be made so by putting a lock on the evaluate(double) method.

Since:

14 Jun 2012

Author:

Mark Taylor

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class JELFunction.XResolver
This public class is an implementation detail, not intended for external use.

Constructor Summary

Constructors
Constructor Description

JELFunction(java.lang.String xvarname, java.lang.String fexpr)
Constructor.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`double`	`evaluate(double x)`	Evaluates this function at a given value of the independent variable.
`java.lang.String`	`getExpression()`	Returns the text of the function expression.
`java.lang.String`	`getXVarName()`	Returns the name of the independent variable.
`static void`	`main(java.lang.String[] args)`	Main method tests this class.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - JELFunction
```
public JELFunction(java.lang.String xvarname,
                   java.lang.String fexpr)
            throws gnu.jel.CompilationException
```
    Constructor.
    
    Parameters:
    
    xvarname - name of the independent variable (for instance "x")
    
    fexpr - text of expression giving the function value, in terms of xvarname (for instance "x+1")
    
    Throws:
    
    gnu.jel.CompilationException
- Method Detail
  - evaluate
```
public double evaluate(double x)
```
    Evaluates this function at a given value of the independent variable. In case of an evaluation error of some kind, NaN is returned.
    
    Parameters:
    
    x - variable value
    
    Returns:
    
    function value
  - getXVarName
```
public java.lang.String getXVarName()
```
    Returns the name of the independent variable.
    
    Returns:
    
    x variable name
  - getExpression
```
public java.lang.String getExpression()
```
    Returns the text of the function expression.
    
    Returns:
    
    function expression
  - main
```
public static void main(java.lang.String[] args)
```
    Main method tests this class. Args are varname, expr, varvalue, for instance "x", "3x+1", "29"