From 8664ba18c7c56bc463f69dd5b131b4071612d567 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Mon, 17 Dec 2018 09:54:14 -0800 Subject: [PATCH] Improve flatten-tree performance MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit * lisp/subr.el (flatten-tree): Improve performance by calling ‘cons’ once rather than twice when a cons cell is popped. --- lisp/subr.el | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/lisp/subr.el b/lisp/subr.el index 7a7c175db4a..3dec6cf66c3 100644 --- a/lisp/subr.el +++ b/lisp/subr.el @@ -5460,14 +5460,14 @@ elements are removed. TREE can be anything that can be made into a list. For each element in TREE, if it is a cons cell return its car recursively. Otherwise return the element." - (let (elems) - (setq tree (list tree)) - (while (let ((elem (pop tree))) - (cond ((consp elem) - (setq tree (cons (car elem) (cons (cdr elem) tree)))) - (elem - (push elem elems))) - tree)) + (let (elems) + (while (consp tree) + (let ((elem (pop tree))) + (while (consp elem) + (push (cdr elem) tree) + (setq elem (car elem))) + (if elem (push elem elems)))) + (if tree (push tree elems)) (nreverse elems))) ;; Technically, `flatten-list' is a misnomer, but we provide it here -- 2.39.5