On Tue, Mar 27, 2018 at 03:27:07AM -0600, Jonathan M Davis via
Digitalmars-d-learn wrote:
>
> Because scope has mostly done nothing (it only affected delegates), in has
> effectively been const without scope for its entire existence in D2 in spite
> of the fact that it was supposed to be the same as const scope. Now that DIP
> 1000 is being implemented, and scope is actually going to do something for
> more than just delegates, it was deemed too dangerous to have in suddenly
> really mean both scope and const, because it would potentially break a lot
> of code. So, in order to prevent such breakage, in was changed to officially
> only mean const instead of const scope. So, what it's meant in practice
> hasn't really changed, but the spec has.
>
> https://issues.dlang.org/show_bug.cgi?id=17928
>
> - Jonathan M Davis
>
FWIW, this is very much my opinion, but if I am understanding this
correctly, the difference between the two prototypes below, that I just
happened to be working on, (assuming they are equivalent with the old
'in' behavior) is the difference between D being really great and D
being 'meh' and not much better than C++ syntax wise.
void copyFrom( in size_t baseIndex, in WFFRecord from, in size_t[] args )
vs.
void copyFrom( scope const size_t baseIndex, scope const WFFRecord from, scope
const size_t[] args )*
For me, I think the second is so much worse for two reasons:
1) The prototype is obfuscated in attribute puke and those extra few
moments to separate the attributes from the parameters bring back
memories of C++ and needing to put parameters on their own lines.
2) It's approaching the line length that just works all the time
with whatever editor I'm in.
I really hope that a better solution to 'in' is found. I'd greatly
prefer breaking code (at compile time) and forcing it to be better code,
but my programs are short and easy to update.
Actually, if arguments to functions were default "logically input"
meaning that they couldn't be changed, returned, and the compiler could
make smart optimizations and pass by reference or value, etc that would
be way better than needing any annotation at all. (Also @safe and maybe
pure by default too, :) I'd rather opt-in to the 'this' context
pointers)
* I realize that scope is redundant but I'm not going to remember all
the specific "rules" about it when I want to say that the argument is
an INPUT and don't mutate or allow it to be be mutated it in ANY
surprising way.
Brian
