Module Cov_const

module Cov_const: sig .. end

The covariance is defined as:

k(x, y) = 1/s^2 logtheta = log(s)

module Params: sig .. end

module Eval: Eval 
    with type Kernel.params = Params.t 
    with type Inducing.t = int 
    with type Input.t = unit 
    with type Inputs.t = int

module Deriv: Deriv 
    with module Eval = Eval 
    with type Hyper.t = [ `Log_theta ]