Assume you have a lovely cousin. She write a good program. But--- oh no, she wrote in c language. You hate c. Assume your cousin quit from the job. She become novelist. Now you want to maintain, develop, improve your cousin's program. You are great in C++ but no C. The source code is 6 MB size in zip format. Just think about it... ok....
What will you do?
1. Forget it, it is stupidly hard to port c program into c++ program....
2. port it, rewrite the program into C++.....
3. Mix it, The base in c, but you improve with new code in c++.....
What is the reason?
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