Thereafter, if you wish to make various interpolations, you need to call the function

splint(double x[], double y[], double y2a[], int n, double x, double *y)

which takes as input the tabulated values \( x[0,..,n - 1] \) and \( y[0,..,n - 1] \) and the output y2a[0,..,n - 1] from spline. It returns the value \( y \) corresponding to the point \( x \).