Re: elisp newbie: simplifying from cl structures?

[John Mastro]

Tory S. Anderson <torys.anderson@gmail.com> wrote:

> (defun change-smtp ()
>   "Change the SMTP server according to the current from line."
>   (save-excursion
>     (loop with from = (save-restriction
>             (message-narrow-to-headers)
>             (message-fetch-field "from"))
>       for (address server . port) in smtp-accounts
>       if (string-match address from) (return (apply 'set-smtp server port
> address)))
>     (error "Cannot infer SMTP information.")))

Try this (untested, sorry):

    (defun change-smtp ()
      "Change the SMTP server according to the current from line."
      (save-excursion
        (cl-loop with from = (save-restriction
                               (message-narrow-to-headers)
                               (message-fetch-field "from"))
                 for (address server port) in smtp-accounts
                 if (string-match address from)
                 return (funcall 'set-smtp server port address))
        (error "Cannot infer SMTP information.")))

I think there were three issues:

1. return is a cl-loop keyword, so it shouldn't be in parenthesis
   as if it were a function. That's the error you were getting.

2. The use of apply needed to change to funcall

3. And then it made sense to change from `for (address server . port)'
   to `for (address server port)'. The difference (given the shape of
   smtp-accounts) is that, in the former case, port will be a list
   containing a single integer, whereas in the latter case it will be an
   integer.

I also changed `loop' to `cl-loop', as is now preferred.

-- 
john