enjoy_circle.c

#include<stdio.h>
#include<math.h>

typedef struct {
  double x;
  double y;
} position;

void print_position(position pos){
  printf("(%.1lf, %.1lf)\n", pos.x, pos.y);
}

double dist_pos(position pos1, position pos2){
  double diffx = pos1.x - pos2.x;
  double diffy = pos1.y - pos2.y;
  return sqrt(diffx * diffx + diffy * diffy);
}

typedef struct {
  position center;
  double radius;
} circle;

void print_circle(circle cir){
  printf("<(%.1lf, %.1lf) %.1lf>\n", cir.center.x,
	 cir.center.y, cir.radius);
}

double area_circle(circle cir){
  return cir.radius * cir.radius * M_PI ;
}

int circle_include_pos(circle cir, position pos){
  return cir.radius > dist_pos(cir.center, pos);
}

int main( void ){
  /* 座標を管理できるようにする */
  position pos1 = {0.0, 0.0};
  position pos2 = {2.0, 0.0};
  print_position(pos1);
  printf("距離：%.1lf\n", dist_pos(pos1, pos2) );

  /* 円を作って表示 */
  position pos_for_circle = {0.0, 0.0};
  circle cir1 = { pos_for_circle, 2.0 };
  print_circle(cir1);

  /* 面積だす */
  printf("面積：%.1lf\n", area_circle(cir1) );
  /* ある点が円の領域内かどうかを調べる */
  pos1 = (position){2.0, 2.0};
  if( circle_include_pos(cir1, pos1) ){
    printf("include!!!\n");
  }else{
    printf("not include!!!\n");
  }
  
  return(0);
}