// Three type aliases for structure types
type Shape = struct { name: string;
                      area: float };
type Circle = struct { name: string;
                       area: float;
                       radius: float };
type Square = struct { name: string;
                       area: float;
                       side: float };

// Function that takes a structure as argument
fun displayShape(shape: Shape): unit = {
    print("Name: ");   print(shape.name);
    print("; area: "); println(shape.area)
};

// Structure constructors
let c: Circle = struct { name = "Circle";
                         area = 10.0f * 10.0f * 3.14f;
                         radius = 10.0f };
let s: Square = struct { name = "Square";
                         area = 2.0f * 2.0f;
                         side = 2.0f };
let r: struct {name: string; area: float} =
    struct { name = "Rectangle";
             area = 3.0f * 4.0f;
             width = 3.0f;
             height = 4.0f };

// Function calls with structures as arguments.  Note: the structures
// passed as arguments have more fields than required by the function.
displayShape(c);
displayShape(s);
displayShape(r);

// Assignment to structure fields
c.area <- s.area <- r.area <- 0.0f;
assert(c.area = s.area);
assert(s.area = r.area);
assert(r.area = 0.0f)