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Re: Programmatic let
From: |
Grégoire Jadi |
Subject: |
Re: Programmatic let |
Date: |
Wed, 05 Dec 2012 21:37:59 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3.50 (gnu/linux) |
Lluís <address@hidden> writes:
> My elisp foo is quite poor, so this might well be a completely stupid approach
> to the problem.
>
> I have a callback that gets automatically called, and uses some
> orgmode-specific
> routines whose behaviour can be tuned through some customizable variables.
>
> The usual approach in orgmode is:
>
> (let ((org-v1 ...) (org-v2 ...)) (org-func ...))
>
> As my function is automatically called (as a response to the D-Bus message),
> I'd
> like to let the user specify a let-like form to let her temporarily override
> the
> behaviour of the `org-func' that my package invokes:
>
> (setq my-cb-org-vars '((org-v1 ...) (org-v2 ...)))
> (defun my-cb (...)
> (programmatic-let my-cb-org-vars
> (org-func ...)))
>
> Is it possible to implement `programmatic-let'? And if so, can you throw me a
> pointer to the appropriate docs?
You could use progv:
> (progv SYMBOLS VALUES &rest BODY)
>
> Bind SYMBOLS to VALUES dynamically in BODY.
> The forms SYMBOLS and VALUES are evaluated, and must evaluate to lists.
> Each symbol in the first list is bound to the corresponding value in the
> second list (or to nil if VALUES is shorter than SYMBOLS); then the
> BODY forms are executed and their result is returned. This is much like
> a `let' form, except that the list of symbols can be computed at run-time.
However, given a defined set of variables, you could parse
my-cb-org-vars yourself:
(defvar my-cb-org-vars '((x ...) (y ...)))
(defun my-cb (...)
(let ((x (cdr (assoc 'x my-cb-org-vars)))
(y (cdr (assoc 'y my-cb-org-vars))))
....))
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