On 2016-11-28 12:24, Eli Zaretskii wrote:
>> From: Tino Calancha <tino.calancha@gmail.com>
>> Date: Mon, 28 Nov 2016 18:52:36 +0900
>> Cc: tino.calancha@gmail.com
>>
>> how about following patch?
>> It prevent some duplication of code in subr.el, and it adds
>> a new test.
> 
> What about the overhead of a function call?  These functions are
> likely to be invoked in loops.
> 
> Should we make the common part a defsubst?

Would defsubst be enough? I think you'd want a defmacro.  Otherwise, you'll still pay for all the funcalls to #'car and #'cdr, won't you?