Comment by jtolmar

Same, and even more so if it's something that feels like it should be in the library code in the first place.

My most copy-pasted code is projecting a point onto a line segment. I end up needing it all the time, it's never in whatever standard library for vector math I'm using, and it's faster to find on SO than to find and translate the code out of whatever my last project that needed it is. Way faster than re-deriving it.

Your vector math library is probably already code imported from random strangers, likely even imported by random strangers, so adding one more function from a random stranger feels entirely appropriate.