A Discussion of Tuple Syntax

[Michel Fortin]

On 2013-08-21 16:59:17 +0000, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:

> On 8/20/13 8:25 PM, Michel Fortin wrote:
>> On 2013-08-21 00:38:30 +0000, Andrei Alexandrescu
>> <SeeWebsiteForEmail at erdani.org> said:
>> 
>>> 1. What do we need?
>> 
>> I think D needs less tuples. It has two kinds (language kind and
>> Phobos's kind), which is confusing. It should have just one that covers
>> most use cases.
> 
> Yah, fewer tuples (or assigning distinct names to what we call today 
> such) would be awesome.

That seems like the only thing everyone agrees with. :-)


> I'm unfortunately lost already. I was discussing tuples as in 
> "anonymous structs", not as in "template tuples".

Well, the original post that started this discussion talked about both. 
I don't think narrowing it only to "anonymous structs" is going to 
solve the syntax problem as a whole.


>>      int a, b, c, d, e, f;
>>      swap(...(a, c, e), ...(b, d, f));
> 
> This looks like an example taken from a book in which "..." means some 
> stuff is omitted.

Seriously, the major issue with tuples is a conceptual one. No pretty 
syntax is going to fix it alone. Unfortunately, talking about concepts 
requires inventing a syntax for them. The syntax then immediately get 
dismissed as ugly/impractical and no thought is given to what's under 
it. No wonder this is getting nowhere for the nth time when everyone 
thinks so superficially.

Just disregard the "..." syntax. It makes sense in the context of my 
other post. There's no way to appreciate it without that context (and 
even then, it can surely be improved).

The idea (in my other post) was to un-cripple language-level tuples 
with one simple fundamental change: allow them to be packed and 
expanded. With that you can cover 99% of what you want from a tuple 
struct using the built-in language-level tuple. Plus you can do some 
other things like the swap of aliases to variables shown above.

There is no reason for template-argument-tuples to be auto-expanding. 
If you fix that, as I proposed in my other post, you'll almost never 
need a library struct template to represent a tuple anymore. Thus, 
fewer tuples.

-- 
Michel Fortin
michel.fortin at michelf.ca
http://michelf.ca