Re: RAII limitations in D?
On Thu, 2014-08-21 at 19:22 -0700, Timothee Cour via Digitalmars-d-learn
wrote:
What would be a good answer to this article?
http://swiftcoder.wordpress.com/2009/02/18/raii-why-is-it-unique-to-c/
Especially the part mentioning D:{
D’s scope keyword, Python’s with statement and C#’s using declaration all
provide limited RAII, by allowing resources to have a scoped lifetime, but
none of them readily or cleanly support the clever tricks allowed by C++’s
combination of smart pointers and RAII, such as returning handles from
functions, multiple handles in the same scope, or handles held by multiple
clients.
}
The author has clearly not actually used Python. There is nothing that C
++ can do with RAII that you cannot do with Python/context managers/with
statement. Nothing.
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RAII limitations in D?
What would be a good answer to this article?
http://swiftcoder.wordpress.com/2009/02/18/raii-why-is-it-unique-to-c/
Especially the part mentioning D:{
D’s scope keyword, Python’s with statement and C#’s using declaration all
provide limited RAII, by allowing resources to have a scoped lifetime, but
none of them readily or cleanly support the clever tricks allowed by C++’s
combination of smart pointers and RAII, such as returning handles from
functions, multiple handles in the same scope, or handles held by multiple
clients.
}
This morning I was pointing to some deprecated usage of scope mentioned in
docs (EMAIL:scope classes mentioned in tutorials, but deprecated). The pull
request (https://github.com/D-Programming-Language/dlang.org/pull/637/files)
mentions using struct or classes allocated on the stack via
typecons.scoped. However what about the RAII usage mentioned in the above
article that allows C++ to return handles for eg (impossible via scope),
that get deterministically destroyed?
Re: RAII limitations in D?
http://dlang.org/phobos/std_typecons.html#.RefCounted
Re: RAII limitations in D?
On Friday, 22 August 2014 at 02:22:16 UTC, Timothee Cour via Digitalmars-d-learn wrote: What would be a good answer to this article? It's own publication date: Feb 2009. The D struct has changed a lot since then, getting new features (@disable, postblit, more reliable destructor) and bugs notwithstanding is pretty well on point nowadays. All the stuff mentioned in there works now.
Re: RAII limitations in D?
On Thu, Aug 21, 2014 at 7:26 PM, Dicebot via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: http://dlang.org/phobos/std_typecons.html#.RefCounted That doesn't work with classes though; is there any way to get a ref counted class? (and btw RefCounted should definitely appear in http://dlang.org/cpptod.html#raii)
Re: RAII limitations in D?
On Friday, 22 August 2014 at 03:00:01 UTC, Timothee Cour via Digitalmars-d-learn wrote: On Thu, Aug 21, 2014 at 7:26 PM, Dicebot via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: http://dlang.org/phobos/std_typecons.html#.RefCounted That doesn't work with classes though; is there any way to get a ref counted class? (and btw RefCounted should definitely appear in http://dlang.org/cpptod.html#raii) It can be made to work with classes and probably should be. There's no fundamental reason why it can't. It's probably just more complicated. - Jonathan M Davis
Re: RAII limitations in D?
On Friday, 22 August 2014 at 02:22:16 UTC, Timothee Cour via
Digitalmars-d-learn wrote:
Especially the part mentioning D:{
D’s scope keyword, Python’s with statement and C#’s using
declaration all
provide limited RAII, by allowing resources to have a scoped
lifetime, but
none of them readily or cleanly support the clever tricks
allowed by C++’s
combination of smart pointers and RAII, such as returning
handles from
functions, multiple handles in the same scope, or handles held
by multiple
clients.
}
Even for C# those are not really problems. Returning from
functions is not a problem: you just return it and that's it,
because resource management is decoupled from types, the types
have no RAII semantics and you can move them around however you
want. On the other hand, in C# it's very easy to declare a
resource, while in C++ you would need to learn all the black
magic of RAII before you can declare a RAII type. Multiple
handles in the same scope are not frequent, nested if's cause
much more trouble. Handles held by multiple clients are even more
rare, and it's usually easy to figure out lifetime for non-memory
resources.
