Limited operator overloading

  1. struct Vec {
  2.     x int
  3.     y int
  4. }
  6. fn (a Vec) str() string {
  7.     return '{$a.x, $a.y}'
  8. }
  10. fn (a Vec) + (b Vec) Vec {
  11.     return Vec{a.x + b.x, a.y + b.y}
  12. }
  14. fn (a Vec) - (b Vec) Vec {
  15.     return Vec{a.x - b.x, a.y - b.y}
  16. }
  18. fn main() {
  19.     a := Vec{2, 3}
  20.     b := Vec{4, 5}
  21.     println(a + b) // "{6, 8}"
  22.     println(a - b) // "{-2, -2}"
  23. }

Operator overloading goes against V’s philosophy of simplicity and predictability. But since scientific and graphical applications are among V’s domains, operator overloading is an important feature to have in order to improve readability:

a.add(b).add(c.mul(d)) is a lot less readable than a + b + c * d.

To improve safety and maintainability, operator overloading is limited:

  • It’s only possible to overload +, -, *, /, % operators.
  • Calling other functions inside operator functions is not allowed.
  • Operator functions can’t modify their arguments.
  • Both arguments must have the same type (just like with all operators in V).