Re: [Boost-users] converting value before inserting into a list

Alexander Shyrokov wrote:

I want to convert values according to a map before inserting it into the list. What is a proper way to do that? I have this:

map m; vector<int> a,b;

for(vector<int>const_iterator i=a.begin();i!=a.end();++i) b.push_back(m[*i]);

I could use std::copy with std::back_inserter to add elements to b, but how do I convert it first? Should I write my own version of back_inserter for that?

copy(a.begin(),a.end(),my_back_inserter(b,m));

One option is to use std::transform( a.begin(), a.end(), std::back_inserter( b ), F ); where F(x) returns m[x]. boost::bind( &std::map::operator[], &m, _1 ) can give you one such F, or you could write your own. I had the half-baked idea to propose std::map<>::operator() once since a map is-a function (and vice versa) by definition, but never got to it.