On 10-12-2011 15:46, bearophile wrote:
Kenji Hara has created a very nice pull request that implements a first step of
good tuple unpacking syntax for D, that is waiting for review and eventual
improvements.
Walter has said (here: http://d.puremagic.com/issues/show_bug.cgi?id=6365#c26 ) that
"We should step back and figure out what we want to do with tuples in the much more
general case", this means he wants D tuples to be well thought-out to avoid future
troubles, and I agree on this. So here here are my thoughts about one thing (probably the
only one) that I don't like about Kenji Hara proposal.
Currently this D code compiles and works, and I think it's bad/broken/ugly
(http://d.puremagic.com/issues/show_bug.cgi?id=6367 ):
import std.typetuple;
void main() {
TypeTuple!(int, int) f = 10;
assert(f[0] == 10);
assert(f[1] == 10);
}
I think that this broken/bad behaviour is currently present in the proposed
tuple unpacking syntax too:
https://github.com/9rnsr/dmd/commit/0d05ce48ffe4e74f2d1ef04e1e6692a59d9ddb44
46 + auto (i, j) = 10;
47 + assert(i == 10);
48 + assert(j == 10);
This goes against any implementation of tuples I have seen in all other
languages, it's generally not useful, and I think it's going to cause troubles
too. So I suggest to not carry this broken/bad behaviour of typetuples to
tuples too.
And I question this design for typetuples too. Is it a good design? I don't
think so, I'd like to see it removed/disallowed for typetuples too (for
uniformity with tuples too).
And if you want to answer something about static arrays:
int[2] a;
a = 5;
I question that syntax too, elsewhere I have asked that to become a syntax
error, and accept only a slice assignment syntax, more uniform with all other
vector operations:
int[2] a;
a[] = 5;
Bye,
bearophile
Such assignments do seem rather error-prone.
- Alex
