Any reasonably
modern version of
Lisp (including
Emacs Lisp and, of course,
Common Lisp) allows
documentation to be attached to
symbols in the form of documentation strings. This is not quite
literate programming, but it does give a handy way of adding searchable documentation to all you write.
It's particularly easy to document functions: just add the string after the argument list (since this will be followed by other forms to evaluate, even a Lisp without documentation strings will accept the defun, and give the same results when evaluating!):
(defun factorial (n)
"Compute N!
If N is large and your Lisp doesn't have bignums, will overflow"
(if (< n 2) 1 (* n (factorial (- n 1)))))
In Emacs, you can access a function's documentation string with "C-h f", and a variable's documentation string with "C-h v".