This does not sound fun. It's better to work on your side projects with manual coding. You will learn more. Retyping things is inefficient for learning. It's like trying to retype calculus solutions — you don't learn from it. Even if there is an explanation of why the code is written in such a way, you did not come up with it, and you don't know alternative solutions. It is a practice for memorizing, not for building…
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i entirely learned all the math and applied math by working through problems whether myself or copying down from the solutions manual or text book over and over again until it stuck