2009/3/3 Igor R <boost.lists@gmail.com>

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.