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From: Kaz Kylheku <643-408-1753@kylheku.com>
Newsgroups: comp.lang.lisp
Subject: Re: Given string 'a.bc.' -- replace each dot(.) with 0 or 1
Date: Sat, 18 May 2024 21:06:16 -0000 (UTC)
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On 2024-05-18, HenHanna <HenHanna@devnull.tb> wrote:
>
> How can i write this function simply?   (in Common Lisp)
>
> -- Given a string  'a.bc.'   -- replace each dot(.)  with 0 or 1.
>
>         -- So the value is a list of 4 strings:
>                                   ('a0bc0'  'a0bc1'  'a1bc0'  'a1bc1')
>
> -- The order is not important.
>              If the string has 3 dots, the value is a list of length 8.
>
> If the program is going to be simpler,
>                        pls use, e.g.   (a $ b c $)  rather than  'a.bc.'

TXR Lisp:

(defun bindots (str)
  (let* ((s (copy str))
         (ixs (where (op eql #\.) s))
         (n (len ixs)))
    (collect-each ((digs (rperm '(#\0 #\1) n)))
      (set [s ixs] digs)
      (copy s))))

1> (bindots "abc")
("abc")
2> (bindots "a.bc")
("a0bc" "a1bc")
3> (bindots "a.b.c")
("a0b0c" "a0b1c" "a1b0c" "a1b1c")
4> (bindots "a.b.cd.e")
("a0b0cd0e" "a0b0cd1e" "a0b1cd0e" "a0b1cd1e" "a1b0cd0e" "a1b0cd1e"
 "a1b1cd0e" "a1b1cd1e")

-- 
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca