Are there copyrights for parts of the code, such as functions, methods?

Question

Law in IT

For example, a programmer wrote a function (not a full-fledged application, but just some auxiliary useful function), and that he has rights to this code and can prohibit someone from using its function?
Z.Y. I did not write some super-duper function, just a question spontaneously arose))

Answer 1

Copyright exists on intellectual property. However, there is a list of concepts that do not fall under copyright. For example, ideas or concepts, including algorithms.
If you have written a function, then you own the copyright to it as a part of the software, however, at the same time, it is enough to rewrite / modify this function, and you get a completely different function that does the same as yours. The problem of rewriting today. You simply cannot prove that the rewritten function is your function.
If you don't want to be used, don't share.

Answer 2

I take your function and change the names of all the variables, and then I make a tiny change that the code doesn't improve, and maybe even worsen a bit. Prove to me that this is your function, and not written by me?