Dart Unary Minus

int difference = 10 - 3;       // Evaluates to 7
double floatDiff = 10.5 - 2;   // Evaluates to 8.5

int value = 5;
int negated = -value;          // Evaluates to -5
int doubleNegated = -(-value); // Evaluates to 5

class Vector {
  final int x;
  final int y;

  const Vector(this.x, this.y);

  // Overriding binary subtraction
  Vector operator -(Vector other) {
    return Vector(x - other.x, y - other.y);
  }

  // Overriding unary negation
  Vector operator unary-() {
    return Vector(-x, -y);
  }
}

void main() {
  Vector v1 = Vector(4, 5);
  Vector v2 = Vector(1, 2);

  Vector v3 = v1 - v2; // Invokes binary operator -(Vector other)
  Vector v4 = -v1;     // Invokes unary operator unary-()
}