additional c++ sources generating errors in Xcode

I have some source written by one of my colleagues in C++. They are stuffs for numerical analysis. I wish them to be included in my Objective-C/Cocoa project. Building seems not to be accomplished... with a kinda error message:

Undefined symbols for architecture x86_64:
"_calcThomas", referenced from:
      _main in main.o
    ld: symbol(s) not found for architecture x86_64
    clang: error: l开发者_开发技巧inker command failed with exit code 1 (use -v to see invocation)

I'm a novice in Xcode or clang. I have a lot of Xcode documentation, and can't find a related one to solve my own. How to achieve my project to work with c++?

Additionally,

• The original c++ sources are pure c++ code composed of c++ sources and headers.
• They are compiled perfectly in case the project is created only with c++ code template, not with Foundation template.

Thanks hopefully.