opEquals/opCmp returning other types

[Andrei Alexandrescu]

On 3/19/12 10:17 AM, Brian Palmer wrote:
> On Monday, 19 March 2012 at 01:29:50 UTC, H. S. Teoh wrote:
>
>> In C++, for example, you can define operator<() and operator>() in
>> completely arbitrary ways, which means they can be totally unrelated to
>> each other, and return results that have nothing to do with each other.
>> This causes inconsistency in that a<b does not necessarily imply b>a,
>> and vice versa. Which makes for inconsistent code.
>
> While I totally get that concern, I've never really seen it become a
> real issue in any of the large C++ systems I've worked on. Maybe I've
> just been lucky? Ruby also allows these arbitrary operator
> redefinitions, and it's never been an issue in the large Ruby systems
> I've worked on, either. Python also allows them, though I don't have
> much Python experience.

I think the concern is not bugs in the implementation, but instead a lot 
of boilerplate text (e.g. in the C++ standard) and code (all of those 
mind-numbing one-liners that swap parameter order etc).

> In fact, a lot of the most useful DSLs in Ruby rely heavily on being
> able to do these overrides. I think D today is missing out on a lot of
> those possibilities.

For D, hooking built-in operators is a poor way to implement DSLs. Best 
is to use strings, CTFE, and mixin.


Andrei