If the subset of feature that I need can be written in the amount of time it would take me to read thru and internalize the library, I'll just write it from scr

If the subset of feature that I need can be written in the amount of time it would take me to read thru and internalize the library, I'll just write it from scratch. Then if there's a problem with it, my team and I will already have a good understanding of the code, instead of discovering that the library is in fact crap (which they often turn out to be). Then if it's something that doesn't really matter and the library code is pedestrian (a logging library), I'll use the library. If it's something that matters a lot and it's expert knowledge and is a large body of work (a complex math/compression/crypto library), I'll use the library.