class vector    //  Allocated array of doubles

   vector()     // default dimension: 3
   vector(int dim)
   vector(vector &)   // copy constructor
   ~vector()


class matrix   // Allocated array of vectors

   matrix()  // default 3 x 3
   matrix(int rows, int cols = 0)
          // 0 columns: cols = rows, default to square matrix
   matrix(double)   // numbers on diagonal, rest=0
   matrix(matrix &)   // copy constructor

   To raise a matrix M to an integer power n:
      (see DDJ #177, page 86)
    note that the bits in n represent squares of M

      Result = 1;
      for (bit = 0; bit < # bits in n; bit ++)
        if bit in n is set
           Result *= M;
        M = M * M;

class time

   Hours, minutes, seconds  (fractional seconds ?)

   Conversion from HMS to decimal and vice-versa

   time(double)   //  hours

   double()       //  Convert to decimal hours

   operator + -