Re: [boost] [Bind] How do I get bind to deduce the return type of for_each?

19 Apr 2010

      Thomas Jordan wrote:
...
[snip] 
Thanks for the suggestion, Roland, I am sure you could get something like this to work easily enough. However, if I understand correctly your suggestion involves defining a separate functor - myClass - to take the vocType's, and which I guess wraps the inner call to for_each. I had hoped for a more generic solution which doesn't involve the creation of new functors. I was hoping I could accomplish the objective of passing an algorithm into an algorithm jgenerically, just doing everything at point of call using just Boost.bind, the std::algorithms (wrapped) and using if necessary some boost.function functors to help type deduction. Are we saying this isn't possible?
Roland Bock replied:

************************************

Hi Thomas, 

we don't say it isn't possible :-) 

Here you go: 

// ----------------------------------------------------------- 
#include <boost/bind.hpp> 
#include <boost/bind/protect.hpp> 
#include <boost/function.hpp> 
#include <vector> 
#include <iostream> 

using namespace std; 
using namespace boost; 

int initValue = 0; 

class myClass 
{ 
public: 
   myClass(): 
      mValue(initValue) 
   {} 

   myClass(const myClass& rhs): 
      mValue(initValue++) 
   { 
   } 

   void func() 
   { 
      cout << mValue << endl; 
   } 
private: 
   int mValue; 
}; 

typedef vector<myClass> vocType; 
typedef vector<vocType> vovType; 

int main() 
{ 
   vovType vov(10, vocType(10, myClass())); 

   for_each(vov.begin(), vov.end(), 
         bind(for_each< vocType::iterator, function<void (myClass&)> >, 
            bind<vocType::iterator>(&vocType::begin, _1), 
            bind<vocType::iterator>(&vocType::end, _1), 
            protect(bind(&myClass::func, _1)) 
            ) 
         ); 
} 
// ----------------------------------------------------------- 

Please let me know if this is working for you. 

Regards, 

Roland 

**************************************************************

Thanks a lot, Roland, this looks good. I felt there must be some way to do it, but it was just beyond my grasp.

Always learning!

Regards,

Tom.