Re: [Sbcl-help] Why can this trivial cons/destructure not be optimized out?

[Stas B. <sta...@gm...>]

Because SBCL is not smart.

On Thu, Feb 9, 2017 at 5:50 AM, J. Gareth Williams <ga...@te...> wrote:
> Hello,
>
> I was just curious why SBCL would not be able to recognize and optimize out
> the cons, car and cdr calls in this function defintion:
>
>  (declaim (optimize speed (debug 0)))
>
>  (defun foo (a b)
>    (let ((l (cons a b)))
>      (+ (car l) (cdr l))))
>
> I would have thought it could (would?) be simplified to a simple '+' call,
> but it appears it is not.
>
> Is there simply no optimization available that can detect and simplify this,
> or is there a technical or spec-related reason that it can't be done?
>
> Thanks for any insight,
>
> Gareth
>
>
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-- 
With best regards, Stas.