public interface RealFieldUnivariateFunction<T extends RealFieldElement<T>>

An interface representing a univariate real function.

When a user-defined function encounters an error during evaluation, the value method should throw a user-defined unchecked exception.

The following code excerpt shows the recommended way to do that using a root solver as an example, but the same construct is applicable to ODE integrators or optimizers.

 private static class LocalException extends RuntimeException {
     // The x value that caused the problem.
     private final SomeFieldType x;

     public LocalException(SomeFieldType x) {
         this.x = x;
     }

     public double getX() {
         return x;
     }
 }

 private static class MyFunction implements FieldUnivariateFunction<SomeFieldType> {
     public SomeFieldType value(SomeFieldType x) {
         SomeFieldType y = hugeFormula(x);
         if (somethingBadHappens) {
           throw new LocalException(x);
         }
         return y;
     }
 }

 public void compute() {
     try {
         solver.solve(maxEval, new MyFunction(a, b, c), min, max);
     } catch (LocalException le) {
         // Retrieve the x value.
     }
 }
 

As shown, the exception is local to the user's code and it is guaranteed that Apache Commons Math will not catch it.