title: Forcing implementation of an interface without modifying class source file?
body: <p>Is it possible to force the implementation of an interface in C++ without modifying the source file of the class that's gonna be implementing it? For example, suppose I include the source files for my class, but I don't wanna touch its source code, I just want this class to implement an interface I created in the code that included it.</p>
  
  <p>Generalizing even more, is it possible to do it with a binary library, where I don't even know the source code? </p>
  
  <p>The reason I'm doing this is that I want to import classes to my projects but want them to be untouched so people can use them in other codes just by copying the files from my project. I know it should be better to disponibilize the raw unmodified source code of the class in another place and modify it for my project but let's suppose I want to make my project extremely understandable for people who already know the class but don't know my specific interface I added to it.</p>