A Discussion of Tuple Syntax

[Dicebot]

On Wednesday, 21 August 2013 at 00:38:31 UTC, Andrei Alexandrescu 
wrote:
> I think this whole thread is approaching things wrongly. It 
> should be:
>
> 1. What do we need?
>
> 2. What does a solution look like in the current language?
>
> 3. Which parts of the solution are frequent/cumbersome enough 
> to warrant a language change?

Exactly. Though if we want to avoid breaking changes as much as 
possible, maybe it should be more like this:

2. What use cases current language state cover?

3. How it can me remodeled to have less confusing semantics / 
definitions while covering as much old behavior as possible?

I am struggling at (3) because current applications love to 
contradict each other when any relatively simple rule set is 
imagined.

Basically there are 3 distinct (according to allowed usage) cases 
for built-in tuples:

1) pure type-tuple
2) mixed compile-time tuple (literals and other compile-time 
expressions go here)
3) run-time tuple over set of variables/parameters

As far as I can see, covering std.typecons.Tuple in similar way 
is trivial - but re-defining those 3 in a meaningful way is 
really challenging. Maybe you have any opinion as a concept 
author? :P