Hi Thomas,
congrace may be used by writing a wrapper "Expression" to UnivarteFunction:
import org.apache.commons.math3.analysis.UnivariateFunction;
import de.congrace.exp4j.Calculable;
import de.congrace.exp4j.ExpressionBuilder;
public class Expression implements UnivariateFunction {
private Calculable calc = null;
public Expression(String function) throws Exception {
calc = new
ExpressionBuilder(function).withVariableNames("x").build();
}
public double value(double x) {
calc.setVariable("x", x);
return calc.calculate();
}
}
Using this you get the folowing code:
final double relativeAccuracy = 1.0e-10;
final double absoluteAccuracy = 1.0e-10;
UnivariateSolver solver = new RegulaFalsiSolver(relativeAccuracy,
absoluteAccuracy);
Expression exp = new Expression("sin(3*x)");
double root = solver.solve(99999, exp, 9.4, 9.7);
System.out.println("root is " + root + " / " + exp.value(root));
with output:
root is 9.42477796076938 / 1.102182119232618E-15 (= 3*PI)
==> Interpreter may be integrated in commons/math, the same result as my
interpreter.
Now I'll compare the functions implemented in congrace.
Regards Detlef
-------- Original-Nachricht --------
> Datum: Tue, 27 Mar 2012 10:10:41 +0200
> Von: Thomas Neidhart <[email protected]>
> An: Commons Developers List <[email protected]>
> Betreff: Re: [math] Improvement: Interpreter for mathematical expressions
> On Tue, Mar 27, 2012 at 10:06 AM, Thomas Neidhart
> <[email protected]
> > wrote:
>
> > 2012/3/27 "Detlef Günther" <[email protected]>
> >
> >> Hello,
> >>
> >> it would be nice to have an interpreter for mathematical expressions so
> >> that functions may be defined at runtime.
> >>
> >
> [snip]
>
> ah something else I have found that looks quite interesting and may be
> used
> to get inspiration:
>
> http://projects.congrace.de/exp4j/index.html
>
> Thomas
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