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Re: "Backquote constructs" to "splice" values without "eval".
From: |
Oleksandr Gavenko |
Subject: |
Re: "Backquote constructs" to "splice" values without "eval". |
Date: |
Mon, 07 Jan 2013 22:36:23 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux) |
On 2013-01-07, Barry Margolin wrote:
>> I construct TLV (table-len-val) structs in string.
>>
>> Is it possible to omit "eval" from second line by using some sugar code:
>>
>> (setq binstr-len 4)
>> (setq binstr (eval `(unibyte-string ?s binstr-len ,@(make-list binstr-len
>> ?x))))
>> (assert (eq (+ 2 binstr-len) (length binstr)))
>>
>> Another solution:
>>
>> (setq binstr (concat (unibyte-string ?s binstr-len) (make-list binstr-len
>> ?x)))
>>
>> Or "apply" stands for this purpose(??):
>>
>> (setq binstr (apply 'unibyte-string ?s binstr-len (make-list binstr-len
>> ?x)))
>
> The "apply" solution is usually the correct way to do it.
I also start thinking about "apply" with several list inside it:
(apply '+ 1 '(2) '(3 4))
But above expression fail (only last arg expanded as list of args). To resolve
this issue I use expression:
(apply '+ 1 (append '(2) '(3 4)))
But how about expression with atoms between (??):
'(1) 2 '(3 4)
I write non-linear code:
(apply '+ (append '(1) (cons 2 '(3 4))))
How to avoid call to "cons"?
--
Best regards!
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