Subroutine fit_cubic

Fit a cubic polynomial to a function given its values ($y_0$ and $y_1$) and its derivative ($y^\prime_0$ and $y^\prime_1$) at two points ($x_0$ and $x_1$)

$$y = ax^3 + bx^2 + cx + d$$

x0, y0, y0p -- real(dp), intent(in)

$x_0$, $y_0$, $y^\prime_0$

x1, y1, y1p -- real(dp), intent(in)

$x_1$, $y_1$, $y^\prime_1$

coeffs -- real(dp), intent(out), dimension(4)

(/a,b,c,d/)

logical_array_print subroutine