example.lox

// functions, control flow, recursion
fun factorial(n) {
  var res = 1;
  for (var i = 2; i <= n; i = i + 1) {
    res = res*i;
  }
  return res;
}

fun fib(n) {
  if (n==0) return 0;
  if (n==1) return 1;
  return fib(n-1)+fib(n-2);
}

// Classes
class Rectangle {
  init(x, y) {
    this.x = x;
    this.y = y;
  }

  perimeter() {
    return this.x*this.y;
  }
}

// Inheritence
class Square < Rectangle {
  init(side) {
    super.init(side, side);
  }
}

// Closures, lexical scope

// A function which returns functions which build rectangles with a constant x
fun x_rectangle(x) {
  fun y_rectangle(y) {
    return Rectangle(x, y);
  }

  return y_rectangle;
}

fun main() {
  print factorial(5);
  print fib(10);
  // Rectangle
  var a = Rectangle(5, 10);

  // Square
  var b = Square(5);

  // Rectangles where x is always 3
  var three_rectangle = x_rectangle(3);

  var c = three_rectangle(4);
  var d = three_rectangle(5);

  // printing
  print "Perimeter of rectangle(5, 10) is:";
  print a.perimeter();

  print "Perimeter of square(5) is:";
  print b.perimeter();

  print "Perimeter of rectangle(3, 4) is:";
  print c.perimeter();

  print "Perimeter of rectangle(3, 5) is:";
  print d.perimeter();
}

main();