c++ - boost::bind to concatenate strings in std::transform -

i trying concatenate 2 string using boost::bind inside std::transform

assuming class has 2 methods 2 strings (first , second) , conatiner vector of strings, trying follows

struct myclass {    std::string getfirststring() {return string1}    std::string getsecondstring() {return string2}     private:      std::string string1;      std::string string2; }  myclass myobj;  std::vector<string > newvec; std::vector<myobj> oldvec; std::transform (oldvec.begin(), oldvec.end(), std::back_inserter(newvec), boost::bind(&std::string::append,boost::bind(&getfirststring,  _1),boost::bind(&getsecondstring, _1 ) ) );  

but, error saying

error: cannot call member function 'virtual const getsecondstring() ' without object 

what missing here?

you have 2 problems.

the first you're taking address of member function incorrectly. have specify class, i.e. boost::bind(&myclass::getfirststring, _1).

the second you're trying bind std::string::append, modifies object it's called on. want operator +. since can't bind directly, use std::plus<std::string> instead. should like:

std::transform(oldvec.begin(), oldvec.end(),                std::back_inserter(newvec),                boost::bind(std::plus<std::string>(),                            boost::bind(&myclass::getfirststring, _1),                            boost::bind(&myclass::getsecondstring, _1)                           )               ); 

or can use boost.lambda instead. , while you're @ it, use boost.range, it's awesome.

namespace rg = boost::range; namespace ll = boost::lambda; rg::transform(oldvec, std::back_inserter(newvec),               ll::bind(&myclass::getfirststring, ll::_1) +                   ll::bind(&myclass::getsecondstring, ll::_1));