Re: Using "internal" macros of a CL implementation

Pascal Costanza <pc@xxxxxxxxx> wrote:
+---------------
| Victor Kryukov wrote:
| > my question was how one can possibly access such macros
| > (even in non-portable way) to avoid duplicating existing functionality.
....
| In a portable way: Create your own package with a low-level API. Make
| sure that the API is close to at least one or ore existing low-level
| APIs. Then you can provide different implementations depending on each
| implementation, and in some implementations simply make the existing one
| available through your own package. There exist numerous compatibility
| layers that do it like this, like ACL-Compat, LW-Compat,
| trivial-garbage, Closer to MOP, and various others. (For example, CLiki
| has a page for such compatibility layers.)
+---------------

Victor, here's a classic example of what Pascal's talking about:

;;; GETENV -- Mostly-portable code for accessing Unix
;;; (or Windows?) environment variables. Morphed very slightly
;;; from <URL:http://cl-cookbook.sourceforge.net/os.html>
;;; Copyright (c) 2002 The Common Lisp Cookbook Project
;;; See: <URL:http://cl-cookbook.sourceforge.net/license.html>
(defun getenv (name &optional default)
(or
#+CMU (cdr (assoc name ext:*environment-list* :test #'string=))
#+Allegro (sys:getenv name)
#+CLISP (ext:getenv name)
#+ECL (si:getenv name)
#+SBCL (sb-unix::posix-getenv name)
#+LISPWORKS (lispworks:environment-variable name)
default))


-Rob

-----
Rob Warnock <rpw3@xxxxxxxx>
627 26th Avenue <URL:http://rpw3.org/>
San Mateo, CA 94403 (650)572-2607

.

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