What's the equivalent of foldr, foldl in Emacs Lisp?

Question

What's the equivalent of foldr, foldl in Emacs Lisp?

Answer 1

Since Emacs-24.3 we recommend the use of cl-lib over cl (which is planned for removal in some distant future), so it would be:

(require 'cl-lib)
(cl-reduce #'+ '(1 2 3 4))

and since Emacs-25, you can also use the seq package for that:

(require 'seq)
(seq-reduce #'+ '(1 2 3 4) 0)