On 9/19/14, 8:14 PM, Timon Gehr wrote:
On 09/20/2014 02:29 AM, Andrei Alexandrescu wrote:
On 9/19/14, 5:28 PM, Timon Gehr wrote:
On 09/19/2014 04:59 PM, Andrei Alexandrescu wrote:
On 9/18/14, 10:53 PM, bearophile wrote:
Andrei Alexandrescu:
Wyatt:
(I wouldn't consider the cookie parameter a better solution; I would
consider it a wart.)
That's the right solution.
The cookie parameter is a ugly wart.
No. -- Andrei
Yes.
No. :o) -- Andrei
To substantiate: It does the wrong thing (same typedef for same base
type) by default and doing the right thing (emulating nominal typing)
may require quite some effort in general (e.g. concatenate the mangled
names of all enclosing template instantiations) while remaining
non-modular (those cookie strings are global identifiers).
This is wrong but probably not worth fighting. Consider:
alias A = Typedef!float;
alias B = Typedef!float;
By basic language rules, A and B are identical. Making them magically
distinct would be surprising and would require explanation. It's as if
someone writes:
struct Point { int x, y; }
alias A = Point;
and then later in the same module
alias B = Point;
and complains that the compiler didn't automagically distinguish between
the two.
Human-readable cookies are exactly the solution: distinct human-readable
moniker that distinguish the types.
alias A = Typedef!(float, "dollar");
alias B = Typedef!(float, "euro");
They will be distinct to the human and compiler alone.
I.e. Typedef is fail. Won't use.
Typedef is win. Feel free to not use.
Declaring a new struct and using Proxy,
perhaps encapsulated using a mixin template is less trouble (quick hack,
results in bad error messages):
import std.typecons;
mixin template WorkingTypedef(string i,T,T init=T.init)/+if(...)+/{
// workaround for https://issues.dlang.org/show_bug.cgi?id=13500
mixin std.typecons.Typedef!(T,init);
mixin(`alias `~i~` =Typedef;`);
}
mixin WorkingTypedef!("Name1",int);
mixin WorkingTypedef!("Name2",int,2);
void main(){
Name1 foo;
Name2 bar;
foo=bar; // error
}
Feel free to disagree, but I don't see how one can.
Your argument has been destroyed.
Andrei
