This is a tiny library by Fernando Borretti. It implements analogue of
the UNIX utility which:
POFTHEDAY> (which:which "which")
#P"/usr/bin/which"
POFTHEDAY> (which:which "sbcl")
#P"/Users/art/.bin/sbcl"
POFTHEDAY> (which:which "python3")
#P"/usr/bin/python3"
POFTHEDAY> (which:which "missing-binary")
NIL
That is it. No more, no less. What do you think, when this library can be useful?
By the way, there are many other trivial (but useful) libraries. All of them are marked with a trivial tag on #pofthedday site.