Re: Structural exhaustive matching

[Martin Nowak via Digitalmars-d-learn]

On Tuesday, 21 April 2015 at 15:36:28 UTC, Jadbox wrote:
What's the best equivalent to Rust's structural enum/pattern 
(match)ing? Is it also possible to enforce exhaustive matches? 
Basically, I'm curious on what the best way to do ADTs in D.

If it needs to be really fast, use final switch on the tag of a 
discriminated union.

enum Tag { A, B, C }
struct Val
{
  Tag tag;
  union
  {
    A a;
    B b;
    C c;
  }
}

void too(Val val)
{
  final switch (val.tag)
  {
  case Tag.A: writeln(val.a); break;
  case Tag.B: writeln(val.b); break;
  case Tag.C: writeln(val.c); break;
  }
}