public void TestMoreThatThreeCoefficients()
{
double[] coeffs = { 1, 3, -5, -15, 4, 12 };
double[] validRoots = { -3, -2, -1, 1, 2 };
_mockRoots.Calculate(coeffs).Returns(validRoots);
var solver = new EquationSolver(_mockRoots);
double[] roots = solver.Solve(coeffs);
Assert.That(roots, Is.EquivalentTo(validRoots));
}
public double[] Solve(double[] coeffs)
{
if (coeffs.Length > 3)
{
// PolynomialRoots r = new PolynomialRoots();
// return r.Calculate(coeffs);
return(_rootsEvaluator.Calculate(coeffs));
}
double a = coeffs[0];
double b = coeffs[1];
double c = coeffs[2];
if (Math.Abs(a) < 1e-10) // if (a == 0.0)
{
if (Math.Abs(b) < 1e-10)
{
throw new ArgumentException("No unknowns!");
}
return(new[] { -c / b });
}
var d = b * b - 4 * a * c;
if (d < 0)
{
throw new ArithmeticException("No real roots!");
}
d = Math.Sqrt(d);
var roots = new double[2];
roots[0] = (-b + d) / (2 * a);
roots[1] = (-b - d) / (2 * a);
return(roots);
}