But isn't this stage supposed to be over after school? I mean, i was pushed towards rewriting everything during my school days. We even had a graphic library with 3 functions: create windows, erase windows and paint this pixel. Rewrote printf, malloc and consorts. Once i was allowed to use glibc trees, map and hashtables, i never wrote an already existing function (maybe a ring buffer and a weird linked list)(and rewrote a scikit image filter because I was too dumb at that time to read changelogs and GitHub issues)