text: /* Compile with:
  make LDLIBS='-lm' CFLAGS="-g -Wall -std=gnu11 --ms-extensions" seamlessone
  */
  #include <stdio.h>
  #include <math.h>
  
  typedef struct point {
     double x, y;
  } point;
  
  typedef struct {
      struct point;
      double z;
  } threepoint;
  
  double threelength (threepoint p){
      return sqrt(p.x*p.x + p.y*p.y + p.z*p.z);
  }
  
  int main(){
      threepoint p = {.x=3, .y=0, .z=4};
      printf("p is %g units from the origin\n", threelength(p));
  }
  