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Re: How to use elisp's closure


From: netawater
Subject: Re: How to use elisp's closure
Date: Tue, 17 Jun 2008 21:06:48 +0800
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux)

David Hansen <address@hidden> writes:

> On Mon, 16 Jun 2008 22:15:21 +0800 netawater wrote:
>
>> In most usual modes, TAB key is bound to an indent function and
>> M-TAB key is bound to a complete symbol function. 
>> I want to write a function if cursor is at the end of word then 
>> try to complete symbol, else indent. It is my function.
>>
>> (defun my-indent-or-complete (M-TAB-func TAB-func)
>> ;;   "If cursor is at the end of word then current mode;s M-TAB 
>> function, else TAB"
>>   (lambda ()
>>     (interactive)
>>    (if (looking-at "\\>")
>>        (apply M-TAB-func '())
>>        (apply TAB-func '())
>>      ))
>>   )
>>
>> Then I try to bound it to \t key:
>>
>> (add-hook 
>>  'find-file-hook 
>>  '(lambda ()
>>     (let ((M-TAB-func (key-binding "\M-\t"))
>>        (TAB-func (key-binding "\t"))
>>        )
>>      (local-set-key 
>>       "\t" 
>>       (my-indent-or-complete M-TAB-func TAB-func)))
>>     )
>>  )
>>
>> However it does not work, it says Symbol's value as variable 
>> is void: TAB-func. I think it is because my function is not
>> a closure, but how can I resolve it?
>>
>
> Elisp is a pretty old lisp dialect...  There are no closures.  The
> `lexical-let' macro from the `cl' package emulates them.  But in your
> case just make `M-TAB-fun' and `TAB-fun' buffer local:
>
> (defvar foo-var default-val)
> (make-variable-buffer-local 'foo-var)
>
> or
>
> (defvar foo-var default-val)
>
> (add-hook 'my-mode-hook #'(lambda ()
>                             (set (make-local-variable 'foo-var) val)
>                             ;; ...
>                             ))
>
> David

Thanks and besides variable is buffer local but local-set-key will bound
key for mode, so I modify my code like this:
(add-hook 
 'find-file-hook 
 '(lambda ()
    (if (eq (key-binding "\t") 'my-indent-or-complete)
      (local-unset-key "\t")
      )
    (set (make-local-variable 'M-TAB-func) (key-binding "\M-\t"))
    (set (make-local-variable 'TAB-func) (key-binding "\t"))
    (local-set-key "\t" 'my-indent-or-complete)
    )
 )

It maybe not a perfect solution, but it works, :)


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