Re: running function in hook dependent on value of a variable

[Kevin Rodgers]

On 6/13/13 8:26 AM, Rainer M Krug wrote:
> Hi
>
> I want to run a function in a hook only if the value of a variable is
> non-nil. I have gotten that far with my less then rudimentary lisp knowledge:
>
> ,----
> | (defvar org-babel-tangle-run-postTangleScript nil
> |   "If non-nil, postTangleScript.sh will be executed")
> | (put 'org-babel-tangle-run-postTangleScript 'safe-local-variable 'booleanp)
> |
> | (defun org-babel-run-post-tangle-script ()
> |   (if org-babel-tangle-run-postTangleScript
> |       (       (message "running the postTangleScript.sh bash shell script")
> |       (shell-command "bash ./postTangleScript.sh"))))
> |
> | (add-hook 'org-babel-post-tangle-hook 'org-babel-run-post-tangle-script)
> `----
>
> But something is wrong with the function, as it does not work.

The THEN clause of the `if' special form is a single expression, but you have
a list of expressions: ((message ...) (shell-command ...))

> Any suggestions?

(defun org-babel-run-post-tangle-script ()
  (if org-babel-tangle-run-postTangleScript
      (progn
        (message "running the postTangleScript.sh bash shell script")
        (shell-command "bash ./postTangleScript.sh"))))

Or for old-school Lisp minimalists:

(defun org-babel-run-post-tangle-script ()
  (and org-babel-tangle-run-postTangleScript
       (messagea "running the postTangleScript.sh bash shell script")
       (shell-command "bash ./postTangleScript.sh")))

Or for CLtL style aficianados like myself:

(defun org-babel-run-post-tangle-script ()
  (when org-babel-tangle-run-postTangleScript
    (message "running the postTangleScript.sh bash shell script")
    (shell-command "bash ./postTangleScript.sh")))

--
Kevin Rodgers
Denver, Colorado, USA