void schint(double *Psi, double *Psip, int k1, int k2, double Veff[], double E,
double r[], double dr[], int N);
The first step in making a Schrödinger solver is to integrate the
Schrödinger equation with a given energy E. Following your
Poisson solver as a guide, design a routine ``schint'' with the above
prototype which (1) takes Psi and Psip as the values of 
and
, respectively, at the point r[k1], (2) integrates the
Schrödinger equation to the point r[k2] using Runge-Kutta, and (3)
returns in Psi and Psip the final values of and .
As you design this routine, you will encounter several issues for which you will find help and suggestions below.