Re: [Boost-users] [boost-users][bind] binding std::for_each

Subject: Re: [Boost-users] [boost-users][bind] binding std::for_each
From: Roman Perepelitsa (roman.perepelitsa_at_[hidden])
Date: 2009-03-04 03:39:08

2009/3/3 Igor R <boost.lists_at_[hidden]>

> Hello,
>
> I'd like to bind std::for_each with some other functor created on the
> fly, like this:
>
> struct A
> {
>  void f(int, int);
> };
>
> vector<shared_ptr<A> > vec;
>
> void f(function<void(void)>);
>
> // I want to call f() with a functor that would call A::f for every
> element in vec
>
> f(bind(&for_each, vec.begin(), vec.end(), bind(&A::f, _1, 1))); //
> doesn't compile
>
> f(bind(&for_each, vec.begin(), vec.end(), protect(bind(&A::f, _1,
> 1)))); // also doesn't compile
>

That's what lambda algorithms are for.

#include <vector>
#include <boost/lambda/algorithm.hpp>
#include <boost/lambda/lambda.hpp>
#include <boost/lambda/bind.hpp>

struct A {
  void f() {}
};

int main() {
  using namespace boost::lambda;
  std::vector<A> v;
  bind(ll::for_each(), v.begin(), v.end(), protect(bind(&A::f, _1)))();
}

Unfortunately, lambda::bind does not play well with smart pointers. You can
add one more bind to that expression to extract pointer from shared_ptr or
you can use boost::bind instead of lambda::bind.

#include <vector>
#include <boost/bind.hpp>
#include <boost/bind/protect.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/lambda/algorithm.hpp>

int main() {
  std::vector<boost::shared_ptr<A> > v;
  boost::bind<void>(boost::lambda::ll::for_each(),
                   v.begin(),
                   v.end(),
                   boost::protect(boost::bind(&A::f, _1)))();
}

Roman Perepelitsa.