emacs - 如何区分 org-babel 代码块中的方案方言？

Question

评估此代码(C-c C-c):

#+begin_src scheme
(andmap + '(1 2 3) '(4 5 6))
#+end_src

导致以下 babel 错误:

ERROR: Unbound variable: andmap

原因:babel 使用 Guile 而不是 Racket 评估代码。我如何告诉 Babel 使用 Racket 而不是 Guile 执行代码？

Answer 1

http://terohasu.net/blog/2011-09-08-on-racket-support-in-emacs-org-mode.html介绍一种方法:

When configuring Emacs to set things up I wasn’t familiar with Babel or any of the solutions for evaluating Scheme code under Emacs for that matter. After some looking at Babel and Inferior Lisp, I didn’t manage to configure Babel to invoke Racket for evaluating a code listing. Instead I resorted to replacing the Babel code for Scheme support (in the ob-scheme.el) with basically just the following code:

(defun org-babel-execute:scheme (body params)
  (let* ((tangle (cdr (assoc :tangle params)))
         (script-file 
          (if (string-equal tangle "no")
              (org-babel-temp-file "org-babel-" ".rkt")
            tangle)))
    (with-temp-file script-file
      (insert body))
    (let* ((pn (org-babel-process-file-name script-file))
           (cmd (format "racket -u %s" pn)))
      (message cmd)
      (shell-command-to-string cmd)
      )))

This solution creates a new Racket instance for every evaluation, and hence is not as efficient as an Inferior Lisp based solution (or similar), but it works, is more straightforward, avoids Racket issues such as specifying the correct module context for evaluating the code, and the evaluation context is always “clean” as a new Racket instance is used.