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Re: Programmatically creating functions
From: |
Emil |
Subject: |
Re: Programmatically creating functions |
Date: |
Tue, 28 Oct 2008 13:29:50 -0700 (PDT) |
User-agent: |
G2/1.0 |
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