A small hack to document programs externally

[Alan Schmitt <alan.schmitt@polytechnique.org>]

Hello,

I've just written a small hack to refer to code in other files from an
org-mode buffer, so that the referred code would be copied in the buffer
to be exported when exporting the org buffer. (Our use case is a large
Coq development which we want to document online. Our may constraint is
that we need the documentation to live in files outside the code, yet
still refer to the actual code.)

Here is a small test case showing the approach

--8<---------------cut here---------------start------------->8---
#+OPTIONS: d:RESULTS

* utilities                                                        :noexport:
#+name: fetch
#+BEGIN_SRC emacs-lisp :results raw :var f="foo.v" :var s="Definition" :var n=0
  (defun fetchlines (file-path search-string nb-lines)
    "Searches for the SEARCH-STRING in FILE-PATH and returns the
  matching line and the following NB-LINES."
    (let ((myBuffer (get-buffer-create "fetchTemp")) result)
      (set-buffer myBuffer)
      (insert-file-contents file-path nil nil nil t)
      (goto-char 1)
      
      (setq result
            (if (search-forward search-string nil t)
                (let ((pos-beg (line-beginning-position))
                      (pos-end
                       (if (> nb-lines 0) 
                           (line-end-position nb-lines) 
                         (re-search-forward "\\.$" nil t))
                       ))
                  (buffer-substring pos-beg pos-end))
              ""))
      
      (kill-buffer myBuffer)
      result))
  
  (fetchlines f s n)
#+END_SRC

#+name: wrap-coq
#+BEGIN_SRC emacs-lisp :var text="" :results raw
(concat "#+BEGIN_SRC coq\n" text "\n#+END_SRC")
#+END_SRC

* example
:PROPERTIES:
:results: drawer
:post: wrap-coq(text=*this*)
:END:

#+call: fetch(f="/Users/schmitta/work/hocorecoq/coq/HOC01defs.v", s="Inductive process")

#+RESULTS:
:RESULTS:
#+BEGIN_SRC coq
Inductive process : Set :=
| Send : chan -> process -> process
| Receive : chan -> lvar -> process -> process
| Lvar : lvar -> process
| Gvar : var -> process
| Par : process -> process -> process
| Nil : process.
#+END_SRC
:END:
--8<---------------cut here---------------end--------------->8---

The ~fetch~ function takes as arguments the file where to search, the
string to be searched, and the number of lines to print. If this last
argument is omitted (or equal to 0), then everything until a final dot
('.' followed by a newline) is printed (this corresponds to the end of a
definition or statement in Coq).

Thanks to everyone who answered my recent questions on the list. And if
you have suggestions to improve this (including ways it may already be
doable natively), please don't hesitate to send them.

Best,

Alan