[wmgries]

You can learn a lot by writing your own code to solve problems solved by existing libraries. I always used to do these kind of things when I was in high school; just because I was bored and wanted to code. Plus, there are many reasons you might need to write your own library to replicate functions of an existing library. A great example is when you can't use an available library because of its license (closed source and you're an open sourced project, or open source and you're a closed source project).