DIP19: Remove comma operator from D and provision better syntactic support for tuples

[deadalnix]

Le 23/09/2012 23:52, Nick Sabalausky a écrit :
> Ok, here's a crazy idea:
>
> Do the reasons for explicit tuple-expansion necessarily apply to
> zero- and one-element tuples? I'm not so sure. Suppose we allowed
> implicit expansion on those...
>
> Now I know what you're thinking: That would be an ugly inconsistency
> between tuples of sizes>1 vs<=1. Well, *mechanically* yes, but
> consider this:
>
> *Logically* speaking, is there really any difference between a
> one-element tuple and an ordinary single value? I don't think so, and
> here's why: What is a tuple, logically speaking? Multiple values being
> handled as if they were a single value. So what's a one-element tuple?
> *One* value being handled as if it were one value - which is *is*.
>
> Similarly, a zero-element tuple is logically equivalent to void (or the
> one value a void can have: the value void, a concept which has been
> argued in the past that might be useful for D, particularly in
> metaprogramming). (I admit this is a little weaker than my argument
> for one-element tuples.)
>
> So perhaps zero- and one-element tuples should be implicitly
> convertible back and forth with void and ordinary non-tuple values,
> respectively (polysemous values?), because that's what they essentially
> are.
>

My reflection on the subject for the past month lead me to the same 
conclusion.

> That means (at least I think it means) that things like () or (1) or
> ((1)) require no way to disambiguate between tuple and expression,
> because either way they're the same thing (or at least freely
> convertible).
>

Exactly.