DeepLang

// Algebraic data type for geometric shapes
type Shape [
    Rectangle(width: F64, height: F64),
    Circle(radius: F64),
    Nothing
]

// Interface for area calculation
interface Area {
    fun area(this) -> F64;
}

// Implement Area for Shape using pattern matching
impl Area for Shape {
    fun area() -> F64 {
        match (this) {
            Rectangle(w, h) => { return w * h; }
            Circle(r)       => { return 3.14159 * r * r; }
            Nothing         => { return 0.0; }
        }
    }
}

fun main() -> () {
    let rect: Shape = Rectangle(3.0, 4.0);
    let circ: Shape = Circle(2.5);
    print(rect.area().toString());  // 12.0
    print(circ.area().toString());  // 19.6349
}

12.0
19.6349375