Hi,
I used old emacs version 23.2. When I try to complete a filename in the REPL, it complains:
Symbol's function definition is void: comint-filename-completion
Another function named comint-dynamic-complete-filename is found. But when I replace the function comint-filename-completion with comint-dynamic-complete-filename, the completion-at-point complains "Wrong type argument: listp, t". It seems comint-dynamic-complete-filename doesn't return the right thing for completion-at-point.
And I like the comint-history-isearch-backward-regexp function. You can press M-r to search history commands instead of M-p or M-n.