[ZootAllures91]

Well, for example:

  import std.stdio;

  struct Math(string Op) {
    static auto eval(T, U)(T l, U r) {
      static if (Op == "+")
        return l + r;
      else static if (Op == "-")
        return l - r;
      else static if (Op == "*")
        return l * r;
      else static if (Op == "/")
        return l / r;
    }
  }

  static immutable auto result = Math!("+").eval(1, 2) + Math!("*").eval(3.0, 3.0);

  void main() {
    writeln(result);
  }  
  

You'll never be able to do anything like that in Rust until const generics are not only complete on their own, but also fully compatible with "const fn".

[mhh__]

Assuming I formatted it right, I made your example shorter

  import std;

  template Math(char Op) {
     auto eval(T, U)(T l, U r) {
        static foreach(x; "+-*/") {            
         if (Op == x)
          mixin("return l ", x, " r;");        
        }        
    }
  }

  static immutable result = Math!('+').eval(1, 2) + Math!('*').eval(3.0, 3.0);

  void main() {
    writeln(result);
  }

[ZootAllures91]

Yeah, that works too. I was trying not to get too crazy I guess. And also just show all the various levels of "static".