Function schaffer_n2

pub fn schaffer_n2<T>(param: &[T; 2]) -> T
where
    T: Float + FromPrimitive,

Schaffer test function No. 2.

Defined as

$$ f(x_1,\,x_2) = 0.5 + \frac{\sin^2(x_1^2 - x_2^2) - 0.5}{\left[1 + 0.001(x_1^2 + x_2^2)\right]^2} $$

where $x_i \in [-100, 100]$.

The global minimum is at $f(x_1,\,x_2) = f(0,\,0) = 0$.