On 09/23/2012 10:40 PM, Andrei Alexandrescu wrote:
I discussed this with Walter, and we concluded that we could deprecate
the comma operator if it helps tuples. So I started with this:
http://www.prowiki.org/wiki4d/wiki.cgi?LanguageDevel/DIPs/DIP19
Unfortunately, I started much cockier than I ended. The analysis in
there fails to construct a case even half strong that deprecating the
comma operator could significantly help tuples.
That is because it does not base the discussion on the right
limitations of built-in tuples:
auto (a,b) = (1,"3");
(auto a, string b) = (1, "3");
BTW: the following works
Tuple!(int, string) t2 = t1[0 .. 2];
because of this:
=> (alias this)
Tuple!(int, string) t2; t2._fields = t1[0 .. 2];
=> (tuple assignment)
Tuple!(int, string) t2; t2._fields[0]=t1[0]; t2._fields[1]=t1[1];
Well it essentially
concludes that tuples are mostly fine as they are, and attempts to
embellish them syntactically are marred with unexpected problems.
Nevertheless, I sure have missed aspects all over, so contributions are
appreciated.
- We already use the name 'tuple'. I'd suggest renaming that to
'sequence' or similar. template Seq(T...){ alias T Seq; }
- The empty tuple can well be (), just like 'Seq!()' works without
issues (it is an expression that is also a type). What is wrong with
it?
- How do we expand a sequence into a tuple?
=> (Seq!(1,2,3),)
- What is the calling convention used for passing built-in tuples to
and from functions?
- As tuples are built-in, expansion can be shorter than '.expand'.
foo(1, tup..., 3); ?
- Template tuple parameters? This would work, but...
template Tuple((T...,)){ alias (T,) Tuple; }
void bar(T,(U...,),V...)(T delegate(U) dg, V args){ ... }
void foo(T,(U...,),(V...,))(T delegate(U) dg, V args){
bar!(T,Tuple!U,V)(dg, args);
} // U and V can be passed separately
- Named tuple fields?
(int x, int y) tuple = (1,2);
swap(tuple.x, tuple.y);
