[boost-users][bind] binding std::for_each
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 Thank you.
"Igor R" <boost.lists@gmail.com> wrote in message news:cfe0a3cf0903031205u428d6a7at944b4fcd89001a64@mail.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
Thank you.
As for_each is a template, to take its address you must pass template parameters. As bind return type is unspecified, you would have to wrap inner bind with function. Like this (didn't test): typedef function<void(A*)> Inner; f(bind(&for_each<Vec::interator, Inner>, vec.begin(), vec.end(), Inner(bind(&A::f, _1, 1)))); And note that you should not write such way even if it works if you are going to make it portable between various STL implementetion, because for_each may take additional defaulted parameters. It is better just to express outer bind as an own class with operator(), not as bind.
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.
participants (3)
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Alexander -
Igor R -
Roman Perepelitsa