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

[ponce]

On Sunday, 23 September 2012 at 21:51:35 UTC, Nick Sabalausky
wrote:
>
> *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.

It's informative to look a bit at the Ocaml language:

   - no distinction between 1-tuple and single value:

      # 1;;
      - : int = 1
      # (1);;
      - : int = 1

   - "void" type is called unit and its notation is the empty 
tuple:

      # ();;
      - : unit = ()

   - for some reason tuples can't be indexed in Ocaml