Subject: bug#14769: [PATCH] optimize `concat's literals

From: Noam Postavsky <[email-masked]>
Date: Tue, 18 Jun 2019 21:43:32 -0400

Mattias Engdegård <[email-masked]> writes:

> +    (dolist (arg (cdr form))

> +                   (let ((val (eval arg)))

> +                          ;; Constant arg: concat with previous.
> +                          (setq accum (concat accum val)))))

Hmm, I think the OP's patch is careful not to concat in a loop like
this: it's O(n^2).  I guess for most human written code n is small
enough that it doesn't matter, but I could imagine this slowing
compilation of a very big rx macro.