On Friday, 30 August 2013 at 14:51:40 UTC, Namespace wrote:
On Friday, 30 August 2013 at 12:18:21 UTC, John Colvin wrote:
On Friday, 30 August 2013 at 11:50:20 UTC, Jacob Carlborg
wrote:
On 2013-08-30 12:56, John Colvin wrote:
alias this, but without implicit conversion. It just
implements all the
op**** functions (including opDispatch).
So what's the difference to Typedef, declared just below?
Typedef uses Proxy to do the work. Proxy is a mixing template
for adding in to a struct/class and Typedef is a very simple
struct making use of it to implement a library typedef.
Unfortunately, Typedef is rather lacking as far as being a
typedef is concerned, but that's not due to problems with
Proxy.
What was the initial reason, to move typedef from the language
into the library? I assume, that there is something special
about typedef that can not be done with alias. If so, why was
it moved?
It seems to be a trend, to move incomplete features from the
language into the library (See also scope -> scoped). I do not
like that. :/
I believe typedef was deprecated due to no-one being able to
agree on the semantics (although it's a bit before my time). I
think it needs to come back as a very simple concept:
A type duplication. e.g. typedef int myInt; (or typedef myInt =
int;) creates a new type that is exactly identical to int, but is
a distinct type in the type system.
It should provide *exactly* identical behaviour to e.g. having
two structs with identical contents but different names. E.g.
struct A{}
typedef A tA;
alias A aA;
alias tA atA;
typedef aA taA;
assert(!is(tA == A));
assert(is(aA == A));
assert(is(atA == tA));
assert(!is(taA == atA));
etc....
It's a really basic feature that D ought to have.
