Boost tuple + transform
- by JH
Is it possible to do the following.
Say my boost tuple has <String, int>
I would like to use std::transform + mem_fun to insert only the String element in a corresponding vector. Is it possible or are we required to use a loop and push_back(get<0)
Ie the following doesn't like to compile... (unknown types...)
result.resize(storage.size())
std::transform(storage.begin(), storage.end(), result.begin(), std::mem_fun(&boost::get<0>));
Here is an example (trying one of the comments):
#include <boost/tuple/tuple.hpp>
#include <vector>
#include <string>
#include <algorithm>
int main(int argc, char**argv)
{
std::vector< boost::tuple<std::string, int> > storage;
std::vector< std::string> result;
result.resize(storage.size());
std::transform(storage.begin(), storage.end(), result.begin(), &boost::get<0, boost::tuple<std::string, int> >);
return 0;
}
Output:
g++ test.cpp
/usr/include/boost/tuple/detail/tuple_basic.hpp: In instantiation of `boost::tuples::cons<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, TT>':
/usr/include/boost/tuple/detail/tuple_basic.hpp:151: instantiated from `boost::tuples::element<0, boost::tuples::cons<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, TT> >'
test.cpp:14: instantiated from here
/usr/include/boost/tuple/detail/tuple_basic.hpp:329: error: `boost::tuples::cons<HT, TT>::tail' has incomplete type
/usr/include/boost/tuple/detail/tuple_basic.hpp:329: error: invalid use of template type parameter
test.cpp: In function `int main(int, char**)':
test.cpp:14: error: no matching function for call to `transform(__gnu_cxx::__normal_iterator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>*, std::vector<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, std::allocator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > > >, __gnu_cxx::__normal_iterator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>*, std::vector<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, std::allocator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > > >, __gnu_cxx::__normal_iterator<std::string*, std::vector<std::string, std::allocator<std::string> > >, <unresolved overloaded function type>)'
