Function easom

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

Easom test function

Defined as

$$ f(x_1, x_2) = - \cos(x_1)\cos(x_2)\exp\left(-(x_1 - \pi)^2 - (x_2 - \pi)^2\right) $$

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

The global minimum is at $f(x_1, x_2) = f(\pi, \pi) = -1$.