Thomas Jordan wrote:
Hi, I have been trying to use Boost.bind to create an 'STL algorithm function object' to pass into another, 'higher order,' STL algorithm (e.g., to pass a for_each into a for_each). However, I am struggling to get bind to deduce the correct return type of the for_each function object. I include the relevant bits of the code below.
class myClass { public: int func(){return mValue;} private: int mValue; };
//wrapper for STL for_each struct myForEach { template <typename II, typename F> F operator()(II begin, II end, F function) const { return std::for_each(begin, end, function); } };
typedef vector<myClass> vocType; typedef vector<vocType> vovType;
//overloaded member functions vocType::begin & end typedef vocType::iterator (vocType::*fnPtr)(); typedef const vocType::iterator (vocType::*constFnPtr)() const;
vovType vov(10, vocType(10, myClass()));
main() { for_each(vov.begin(), vov.end(), bind< ? >(myForEach(), bind(static_cast<fnPtr>(&vocType::begin),_1), bind(static_cast<fnPtr>(&vocType::end),_1), protect(bind(&myClass::func, _1))) }
I tried various things for bind<?>, but was only able to get the code to compile (eventually) on my Unix box when I substituted bind< boost::_bi::protected_bind_t<boost::_bi::bind_t<int, boost::_mfi::mf0<int, myClass>, boost::_bi::list1<boost::arg<1> (*)()> > > > for the bind<?>. I had guessed this might work from studying the compiler error messages. Obviously, this is not an ideal solution!
Also, I only used the myForEach wrapper after having first attempted - and similarly failed - to bind the raw STL for_each.
Is there any way I can help bind to deduce the correct return type - for either myForEach or std::for_each, or both?
In my experience it is easier to use a named functor object. Such as function<void (const vocType&)> functor = bind(&myClass::func, _1); std::for_each(vov.begin(), vov.end(), functor); Untested, but I am pretty sure something along these lines will work. Regards, Roland