Can opCmp return a 'long' instead of 'int'?

[Timon Gehr]

On 02/16/2014 04:40 PM, bearophile wrote:
> Timon Gehr:
>
>>     assert(S(1)<S(2)); // passes. ok.
>>     assert(S(int.min)>S(int.max)); // passes. oops.
>
> A possible solution is to add to Phobos (unless it's already there) a
> variadic templated funcion cmpBuilder() that accepts an even number of
> arguments, that are seen as pairs. Usage example:
>
> struct Foo {
>    int x, y;
>    string s;
>    int opCmp(in ref Foo r) {
>      return cmpBuilder(x, r.x, y.abs, r.y.abs, s, r.s);
>    }
> }
>
> Is this worth adding to Phobos?
>
> Bye,
> bearophile

IMO no (lots of repetition), but forwarding opCmp is:

struct Foo{
     int x,y;
     string s;
     private @property order(){ return tuple(x, abs(y), s); }
     mixin OrderBy!order;
}

Furthermore, the language should be updated such that the built-in types 
are not special w.r.t. operators. Eg:

1.opBinary!"+"(2)
1.opCmp(2)

should work.

The following should be supported as well:

struct Foo{
     int x,y;
     string s;
     mixin OrderBy!(()=>tuple(x, abs(y), s));
}

(Currently DMD bans function literals as members.)