Scanl for (emacs) Lisp?

[pgt]

Hi,

surprisingly I couldn't find a function equivalent to scanl in swi-prolog[1]
or even the more sophisticated cascade[2] in UCB Logo. It is a higher
order function on a sequence, a mixture of folding and mapping. The seq,
dash and CL libs do not have it. Listopia, a CL lib has it[3].

One could use such function for example solving the famous trapping rain
water problem. A simple recursive implementation on a list could be: 

(defun scanl (fn lst ini)
  "returns a list of successive reduced values from the left"      
  (named-let scanl ((lst lst)
                    (ini ini)
                    (res nil))
    (if lst
        (scanl (cdr lst)
               (setq ini (funcall fn ini (car lst)))
               (append res (list ini)))
      res)))
      
(scanl #'max '(3 1 4 5 2) 0)

=> (3 3 4 5 5)

Footnotes:
[1]  https://www.swi-prolog.org/pldoc/man?predicate=scanl/4

[2]  https://github.com/jrincayc/ucblogo-code/blob/master/helpfiles/cascade

[3]  https://github.com/Dimercel/listopia#scans

Best regards

-- 
Plamen Tanovski