Re: Pointers to member functions are NOT useless

From:

Jonathan Lee <jonathan.lee.975@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sat, 24 Jul 2010 08:42:08 -0700 (PDT)

Message-ID:

<647bb049-e80e-4a1e-a9be-c6f723e5742a@w12g2000yqj.googlegroups.com>

On Jul 24, 11:10 am, "Francesco S. Carta" <entul...@gmail.com> wrote:

Hi there,
after reading an article complaining that pointers to member functions
are misconceived in C++, and after reading a comment about them saying
that they happen to be a rarely necessary feature - if ever necessary at
all - I decided to investigate them to see how I could take advantage of
them, and I also decided to post this message to get the group's feedback=

..

Not to be a Negative Nancy, but I tend to agree with the position that
pointer to member functions are (nearly) useless. I've never used
them.

The problem is there seem to be more suitable idioms in most cases.
Take your example. I'd rather use polymorphism and write something
like

  void enter(Field f) { current_field = f; }

  void move(Movement m) {
    switch(current_field) {
    case water: return moveWater(m);
    case air: return moveAir(m);
    case ground: return moveGround(m);
    default: throw std::runtime_error("WTField");
    }
  }

and let the derived classes implement moveXXX(). And
it's not like it's just the example you came up with
that this could be done with. I think you could
refactor this whole category of uses.

Though I'd still be interested to see what people
can come up with.

--Jonathan