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  • Re: List of digits->number

    From B. Pym@Nobody447095@here-nor-there.org to comp.lang.lisp,comp.lang.scheme on Fri Jul 18 01:48:08 2025
    From Newsgroup: comp.lang.lisp

    B. Pym wrote:

    Frank Buss wrote:

    (defun split-backward (number &optional (base 10))
    (loop while (< 0 number) collect
    (multiple-value-bind (quotient remainder) (floor number base)
    (setf number quotient)
    remainder)))

    LOOP is ok, but I wonder if there is a more elegant contruct like REDUCE for the opposite concept for building a list. Building the list should not need more program code characters than reducing the list.

    Testing:

    * (split-backward 1984)

    (4 8 9 1)


    Gauche Scheme

    (use srfi-1) ; unfold

    (unfold zero? (cut mod <> 10) (cut quotient <> 10) 1984)
    ===>
    (4 8 9 1)

    (do ((n 1984 (div n 10))
    (r () (cons (mod n 10) r)))
    ((zero? n) r))

    ===>
    (1 9 8 4)
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