Time for action - revisiting the Sel'kov model

1. 1. In Chapter 5, we discussed how to solve a differential equation system using lsode. Specifically, we used lsode to solve the Sel'kov model. There the differential equation system was specified in an m-function, but we can also implement it using the C++ interface. Recall that in the original function, we used the global variable global_b in the function, so the C++ implementation needs to retrieve this variable from the Octave workspace as well.

   Code Listing 8.5
   #include <octave/oct.h> #1
   #2
   DEFUN_DLD(selkovo, argv, , "Usage: y = selkovo(x)"){ #3
   octave_value_list retval; #4
   #5
   octave_value boct = get_global_value("global_b"); #6
   double b = boct.scalar_value(); #7
   #8
   ColumnVector x( argv(0).vector_value() ); #9
   ColumnVector f(2); #10
   #11
   const double *xval = x.fortran_vec(); #12
   double *fval = f.fortran_vec(); #13
   #14
   double xt = 0.1*xval[1] + xval[0]*xval[0]*xval[1]; #15
   #16
   fval[0] = -xval[0] + xt; #17
   fval[1] = b - xt; #18
   #19
   retval...