Revamping the numeric classes

Fergus Henderson
Sat, 10 Feb 2001 16:52:39 +1100

On 08-Feb-2001, Marcin 'Qrczak' Kowalczyk <> wrote:
> I don't like the idea of treating the case "no explicit definitions
> were given because all have default definitions which are OK"
> differently than "some explicit definitions were given".

I don't really like it that much either, but...

> When there is a superclass, it must have an instance defined, so if
> we permit such thing at all, I would let it implicitly define all
> superclass instances not defined explicitly, or something like that.
> At least when all methods have default definitions. Yes, I know that
> they can be mutually recursive and thus all will be bottoms...

... that is the problem I was trying to solve.

> So maybe there should be a way to specify that default definitions
> are cyclic and some of them must be defined?

I agree 100%.

> It is usually written in comments anyway, because it is not immediately
> visible in the definitions.

Yes.  Much better to make it part of the language, so that the compiler
can check it.

> (now any method definition
> can be omitted even if it has no default!),

Yeah, that one really sucks.

Fergus Henderson <>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <>  |     -- the last words of T. S. Garp.