Modifying Numerical Recipes ODE routines

This is the first time that we shall use routines from Numerical Recipes. Often these routines meet our needs directly. However, in this case, the Numerical Recipes routines lack a number of important capabilities. In particular, we must modify these routines to allow us to (a) work in double precision, (b) effect a change of variables, (c) solve equations which involve an function whose values are stored in an array.