#include <math.h>
 
typedef struct { double x, y; } Point;
 
/* define your functions below */
 
Point f1( double t)
{
  Point r;
 
  r.x = t*cos(t);
  r.y = t*sin(t);
 
  return r;
}
 
Point f2( double t)
{
  Point r;
 
  r.x = r.y = t;
 
  return r;
}
 
/* set f to list of function names with 0 at the end */
 
Point (*f[])(double) = { f1, f2, 0};