Calling C++ function from Ruby

I have a Ruby on Rails project that needs to integrate C++ with it. I know that to call a C++ program from Ruby, one can use the Ruby system command to call the C++ make file. system("./make_filename #{parameter} #{parameter}") Right now, I want to call one of the functions in the C++ program but I do not know the proper command. TASK: Your task is simple. Describe to me what are the procedures that I need to do. If the procedures are simple, I will pay you "consultation fees" amounting to $30 to $50. If the procedures are complex,I will hire you to do this task for me. Note: I have had too many service providers pretending to know what to do but eventually failed at their task. Those interested in this, PLEASE MAKE SURE YOU CAN DELIVER THE SOLUTION WITHIN 3 DAYS MAXIMUM. I will not hesitate to cancel the project if you delay your work. On the other hand, those who are able to deliver fast efficient work will be rewarded accordingly.