Re: 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.)