Re: Programmatically creating functions

[Emil <emarceta@gmail.com>]

On Oct 25, 11:28 am, Ian Eure <i...@digg.com> wrote:
> On Oct 21, 2008, at 11:57 AM, Andreas Politz wrote:
>
>
>
> > Joost Diepenmaat wrote:
> >> Ian Eure <i...@digg.com> writes:
> >>> So, I have a list of symbols:
>
> >>> '(foo bar baz)
>
> >>> I want to iterate over the list and create a function from each  
> >>> which
> >>> does something like this:
>
> >>> (defun call-foo ()
> >>>  (interactive)
> >>>  (invoke-stuff 'foo)
>
> >>> How can I accomplish this? I can't figure out how to create the
> >>> function. I've tried a number of approaches, but have not met with
> >>> success.
>
> >>> - eval'ing the defun. Returns a function symbol, but I can't call
> >>> it. Maybe it's only created within the scope of the (eval) and not
> >>> callable from outside?
>
> >>> - Creating a symbol and using fset to assign a lambda to it's
> >>> function cell. It sort of works, but I'm unclear on how to pass a
> >>> variable function name to defun, nor am I clear on how I can make  
> >>> sure
> >>> it calls invoke-stuff with the right symbol.
> >> I'm not /quite/ sure where you've got problems, but in this case  
> >> elisp's
> >> lack of closures hurts. IMHO the simplest way to get what you want  
> >> is to
> >> use a macro:
> >> (defmacro make-caller-macro (symbol)   `(defun ,(intern (concat  
> >> "call-" (symbol-name symbol))) ()      (,symbol)))
> >> But that won't evaluate the argument, so you'd more or less have to  
> >> use
> >> eval as well:
> >> (dolist (s '(foo bar)) (eval `(make-caller-macro ,s)))
>
> > Does this work ? (in general)
>
> Yes, with a little hacking, it works:
>
> (defvar sql-connection-alist
>    '((poola
>       (sql-product 'mysql)
>       (sql-server "pool-a")
>       (sql-user "me")
>       (sql-password "mypass")
>       (sql-database "default")
>       (sql-port 3306))
>      (poolb
>       (sql-product 'mysql)
>       (sql-server "pool-b")
>       (sql-user "me")
>       (sql-password "mypass")
>       (sql-database "default")
>       (sql-port 3307)))
>    "AList of preset connections for `sql-connect-preset'.")
>
> (defun sql-connect-preset (name)
>    "Connect to a predefined SQL connection listed in `sql-connection-
> alist'"
>    (require 'sql)
>    (let ((conn (cdr (assoc name sql-connection-alist)))
>          (sql-name (symbol-name name)))
>      (eval `(let ,conn
>               (flet ((sql-get-login (&rest what)))
>                 (sql-product-interactive sql-product))))))
>
> (defun sql-convenience ()
>    (interactive)
>    (mapcar (lambda (conn)
>              (let ((name (car conn)))
>                (fset (intern (format "sql-%s" name))
>                      `(lambda nil
>                         ,(format "Connect to %s SQL preset." name)
>                         (interactive)
>                         (sql-connect-preset ',name)))))
>            sql-connection-alist))
>
> So now I can define preset connections and get sql-* methods to invoke  
> them directly.


Here is another attempt  I wrote recently :

(setq sql-connection-alist
      '((local
         (sql-product 'mysql)
         (sql-server "<server>")
         (sql-user "<user>")
         (sql-password "<password>")
         (sql-database "<database>")
         (sql-port 3306))
        (qa
         (sql-product 'mysql)
         (sql-server "<server>")
         (sql-user "<user>")
         (sql-password "<password>")
         (sql-database "<database>")
         (sql-port 3306))))

(defun sql-connect-preset (name)
  "Connect to a predefined SQL connection listed in `sql-connection-
alist'"
  (eval `(let ,(cdr (assoc name sql-connection-alist))
    (flet ((sql-get-login (&rest what)))
      (sql-product-interactive sql-product)))))

;; iterate over the alist and create functions
(mapcar '(lambda(x)
	   (let ((ds-name (symbol-name x)))
	     (eval (car (read-from-string
			 (format "(defun sql-%s()  (interactive) (sql-connect-preset '%s))"
ds-name ds-name))))))
	(mapcar 'car sql-connection-alist))

(provide 'mysql-utils)


Require mysql-utils and it i becomes available as M-x sql-local, or M-
x sql-qa.

emil