On Friday, 18 May 2012 at 10:47:11 UTC, Dario Schiavon wrote:
On Thursday, 17 May 2012 at 17:13:50 UTC, deadalnix wrote:
[...]
I think you show a real need here, but I don't really like
your proposal. I'd advocate for recycling the comma operator
for tuple building.
This would be very similar to your proposal as a result, but
no need to introduce a new syntax.
As I see it, creating single-item tuples would still be
difficult with the comma syntax, except by introducing syntaxes
like (a,) or (a,void), which don't look very good. Sure,
single-item tuples don't appear that useful at first, but let's
assume you want to append a new item to the tuple: can you
write anything better than tuple~(a,)? Python's solution is not
very elegant in these cases.
Although, it just came to my mind, appending new items to tuples
is quite easy with the actual rules for AliasTuples. Since
AliasTuples can't have a hierarchy, they always unpack
automatically. So the expression "tuple,a" would actually append
the item "a" to the AliasTuple "tuple". The following works
already in D:
import std.stdio;
import std.typetuple;
void main() {
alias TypeTuple!(1, 2) a;
alias TypeTuple!(a, 3) b; // appends 3 to a
writeln(b); // prints "123"
}
Appending items to tuples actually covers 99% of my needs of
single-item tuples in Python. Can anyone find other needs for
single-item tuples? Or for empty tuples?
However, another point of my post was whether we really need
Records (std.typecons.Tuple's), which take approximately the
same role as traditional struct's after all, to allow returning
multiple values from functions. Wouldn't AliasTuples take on
the role as well?
