For a similar situation today, there is the editor lem which is an Emacs-clone written in Common Lisp (and whose extension language is also Common Lisp).
more generally, though, even if you aren't using a gui library with a built-in text editor widget, gigahertz and gigaflops make it not especially challenging to write a usable text editor in a high-level language. http://canonical.org/~kragen/sw/dev3/edumb.py is 183 lines of fairly straightforward python and includes full-text search and infinite undo; it's not quite usable but pretty close. its really stupid buffer data structure might start to get unresponsive once you're editing a file in the neighborhood of 100k
