#import <Foundation/Foundation.h>
#import <math.h>

@protocol Geometry <NSObject>
- (double)area;
- (double)perim;
@end

@interface Rect : NSObject <Geometry>
@property double width, height;
@end

@implementation Rect
- (instancetype)initWithWidth:(double)width height:(double)height {
    self = [super init];
    if (self) {
        _width = width;
        _height = height;
    }
    return self;
}

- (double)area {
    return self.width * self.height;
}

- (double)perim {
    return 2*self.width + 2*self.height;
}
@end

@interface Circle : NSObject <Geometry>
@property double radius;
@end

@implementation Circle
- (instancetype)initWithRadius:(double)radius {
    self = [super init];
    if (self) {
        _radius = radius;
    }
    return self;
}

- (double)area {
    return M_PI * self.radius * self.radius;
}

- (double)perim {
    return 2 * M_PI * self.radius;
}
@end

void measure(id<Geometry> g) {
    NSLog(@"%@", g);
    NSLog(@"Area: %f", [g area]);
    NSLog(@"Perimeter: %f", [g perim]);
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Rect *r = [[Rect alloc] initWithWidth:3 height:4];
        Circle *c = [[Circle alloc] initWithRadius:5];
        
        measure(r);
        measure(c);
    }
    return 0;
}