Function rgsl::numerical_differentiation::deriv_backward

pub fn deriv_backward<F: Fn(f64) -> f64>(
    f: F, 
    x: f64, 
    h: f64
) -> (Value, f64, f64)

This function computes the numerical derivative of the function f at the point x using an adaptive backward difference algorithm with a step-size of h. The function is evaluated only at points less than x, and never at x itself. The derivative is returned in result and an estimate of its absolute error is returned in abserr. This function should be used if f(x) has a discontinuity at x, or is undefined for values greater than x.

This function is equivalent to calling gsl_deriv_forward with a negative step-size.

Returns (result, abs_err).