Where are g++ stl libraries in Darwin

I am trying to understand how some of the data structures are designed in stl. In ubuntu, I usually open the .h and .cpp files from /usr/local/include but in Darwin (kernel version 14.3.0) I am lost, google doesnt help much either, the file structure is different. So, could you please tell me where are those libraries' .h and .cpp files in mac? P.S. I installed XCode but I didnt like it so I uninstalled it. The g++ stayed even after uninstall. Actually I never tried checking whether g++ was there before I installed Xcode. I dont have /Applications/Xcode.app so it must be someplace else.