• Flaze07 (4/4) Jun 22 2018 recently, I visited the glossary and saw that functor exist in
• Steven Schveighoffer (10/14) Jun 22 2018 D covers a lot of programming paradigms. It has Java-like classes and
• =?UTF-8?Q?Ali_=c3=87ehreli?= (6/7) Jun 22 2018 I wonder whether they are more efficient because a functor would carry
• Steven Schveighoffer (5/14) Jun 22 2018 If it's not a closure, then none. It just uses the stack frame.
• Flaze07 (3/17) Jun 24 2018 I see, thank you
• 12345swordy (2/6) Jun 22 2018 It there for Extern(C++).
• Jonathan M Davis (20/24) Jun 22 2018 D is a multi-paradigm language that has operator overloading, so it pret...

Flaze07 <christianseiji.cs gmail.com> writes:

recently, I visited the glossary and saw that functor exist in 
D...I know that functor exist C++ as a way to easily allow higher 
order function, but since D already has function and delegates, 
is there a point to functor ?

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 6/22/18 10:06 AM, Flaze07 wrote:
 recently, I visited the glossary and saw that functor exist in D...I 
 know that functor exist C++ as a way to easily allow higher order 
 function, but since D already has function and delegates, is there a 
 point to functor ?

D covers a lot of programming paradigms. It has Java-like classes and 
interfaces, and C++-like functors, along with pure functions, (good) 
templates, immutable data, concurrency, etc.

It's meant to make it easy to transition to D from the language you are 
used to.

There's no specific reason to use functors, but if you want to, you can, 
as most of std.algorithm supports them (see 
https://dlang.org/phobos/std_traits.html#isCallable).

-Steve

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 06/22/2018 08:17 AM, Steven Schveighoffer wrote:

 reason to use functors

I wonder whether they are more efficient because a functor would carry 
just the state that it needs. Also, there is no GC memory allocation 
unless the programmer wants to.

I wonder how much state is allocated for a delegate?

Ali

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 6/22/18 2:25 PM, Ali Çehreli wrote:
 On 06/22/2018 08:17 AM, Steven Schveighoffer wrote:
 
  > reason to use functors
 
 I wonder whether they are more efficient because a functor would carry 
 just the state that it needs. Also, there is no GC memory allocation 
 unless the programmer wants to.
 
 I wonder how much state is allocated for a delegate?

If it's not a closure, then none. It just uses the stack frame.

Most of the time you would just use an alias instead of a functor or a 
delegate.

-Steve

Flaze07 <christianseiji.cs gmail.com> writes:

On Friday, 22 June 2018 at 20:20:56 UTC, Steven Schveighoffer 
wrote:
 On 6/22/18 2:25 PM, Ali Çehreli wrote:
 On 06/22/2018 08:17 AM, Steven Schveighoffer wrote:
 
  > reason to use functors
 
 I wonder whether they are more efficient because a functor 
 would carry just the state that it needs. Also, there is no GC 
 memory allocation unless the programmer wants to.
 
 I wonder how much state is allocated for a delegate?

 If it's not a closure, then none. It just uses the stack frame.

 Most of the time you would just use an alias instead of a 
 functor or a delegate.

 -Steve

I see, thank you

12345swordy <alexanderheistermann gmail.com> writes:

On Friday, 22 June 2018 at 14:06:06 UTC, Flaze07 wrote:
 recently, I visited the glossary and saw that functor exist in 
 D...I know that functor exist C++ as a way to easily allow 
 higher order function, but since D already has function and 
 delegates, is there a point to functor ?

It there for Extern(C++).

Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:

On Friday, June 22, 2018 14:06:06 Flaze07 via Digitalmars-d-learn wrote:
 recently, I visited the glossary and saw that functor exist in
 D...I know that functor exist C++ as a way to easily allow higher
 order function, but since D already has function and delegates,
 is there a point to functor ?

D is a multi-paradigm language that has operator overloading, so it pretty
much naturally ends up with functors whether it was specifically planned for
or not, though I'm not sure that they get used all that much. I think that
some folks do use them instead of delegates in some situations, because
delegates allocate closures to hold their state (copying the associated
stack onto GC-allocated memory). So, if you have code that you want or need
to be  nogc, delegates aren't going to work, whereas functors can. The
biggest reason that a lot of Phobos has trouble being used in  nogc code is
because of closures being allocated for lambdas (since lambdas are
frequently delegates), and if someone goes to the extra effort of using
functors instead of lambdas, they can avoid those allocations. But I think
that most folks don't worry about it and just use lambdas. It's the folks
that either actually need  nogc or are just paranoid about the GC that most
typically try to avoid such allocations - though I'm sure that we'd all love
it if the compiler could be a bit smarter about not allocating closures when
they're not actually needed (it's pretty conservative about it, because if
it ever doesn't allocate a closure when one was needed, then you have an
 safety bug).

- Jonathan M Davis