New subject: Annoying coding

20 Jan 2009

      Why not use Boost.Bind? It will bind to data members, returning a functor that accesses that member. E.g.

    boost::bind(&A::a, _1);

will create a functor that takes an instance of A and returns a reference to the a member. You can then pass that to whatever other functor is being used. Something like (not tested!)

    std::accumulate(m.begin(), m.end(), bind(std::add, _1, bind(&std::map::value_type::first, _1));

Boost.Lambda can do this as well, but I am not familiar enough with it to provide an example.

At 07:22 AM 1/20/2009, you wrote:
...
Hi again,
I have a problem. Not really big one but annoying.
Often we need to write code like this:
struct A{
 int a;
 std::string b;
};
int a_sum(int i, const A &v){ return v.a + i; };
std::vector<A> v;
//fill this vector somewhere
std::accumulate( v.begin(), v.end(), 0, a_sum );
or something like
int m_sum(int i, const std::pair p) { return p.first + i; };
std::map   m;
std::accumlate( m.begin(), m.end(), 0, m_sum);
Or in common words we need to write some kind functor which just get
member from element and apply it to another functor.
Of course I can write something like:
template
struct get_mem{
  const V_ &operator()(const T_ &elem){
      return elem->*Ptr_;
  };
};
but may be there is library way to do this?
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Re: [Boost-users] Annoying coding

Alan M. Carroll

Robert Jones

Maxim Koshelev

Robert Jones

Maxim Koshelev

Robert Jones

Maxim Koshelev

Zachary Turner

Robert Jones

Maxim Koshelev

Maxim Koshelev

Robert Jones

Zachary Turner

Robert Jones

Zachary Turner

Maxim Koshelev

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