static switch/pattern matching

[Lodovico Giaretta via Digitalmars-d-learn]

On Saturday, 25 June 2016 at 10:39:09 UTC, John wrote:
> Thanks for the help, both. This appeared to work, until I 
> realised the lambda isn't static:
>
>   void match(T, cases...)() {
>     static if (cases.length == 1) cases[0]();
>     else static if (cases.length > 2) {
>       static if (is(typeof(cases[0]) == bool)) {
>         static if (cases[0]) cases[1]();
>         else match!(T, cases[2 .. $]);
>       }
>       else static if (is(T == cases[0])) cases[1]();
>       else match!(T, cases[2 .. $]);
>     }
>   }
>
>   void test(T)(T value) {
>     int i;
>     string s;
>     match!(T,
>       int, () => i = value,
>       string, () => s = value
>     );
>   }
>
>   test(1);
>   test("A string");
>
> The compiler complains about not being able convert an int to a 
> string and vice versa.

If you want this to work, you need your lambdas to take the 
casted value as a parameter:

    void test(T)(T value) {
      int i;
      string s;
      match!(value,
        int, (val) => i = val,
        string, (val) => s = val
      );
    }

And of course you need to modify match! for this to work.