In Elisp, how to get path string with slash properly inserted?

Question

I am manually constructing path strings in Elisp by concatenating partial paths and directory names. Unfortunately sometimes the paths end with slash, sometimes not. Theref

Answer 1

Something like this should work as a starting point, although you'd want to flesh it out a bit to make it platform independent, etc.

(defun append-path-component (path new-part)
  (if (string-match ".*/$" path)
    (concat path new-part)
    (concat path "/" new-part)))

As per usual, there's probably some bit of elisp that already does this that I'm just not aware of.