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From: HenHanna <HenHanna@devnull.tb>
Newsgroups: comp.lang.lisp
Subject: Re: string chains
Date: Tue, 6 Aug 2024 10:02:30 -0700
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On 8/5/2024 4:34 PM, B. Pym wrote:
>> The task is to somehow implement Amb, and demonstrate it with
>> a program which chooses one word from each of the following
>> four sets of character strings to generate a four-word
>> sentence:
>>
>> "the" "that" "a"
>> "frog" "elephant" "thing"
>> "walked" "treaded" "grows"
>> "slowly" "quickly"
>>
>> The constraint to be satisfied is that the last character of
>> each word (other than the last) is the same as the first
>> character of its successor.
>>
>> The only successful sentence is "that thing grows slowly";
>> other combinations do not satisfy the constraint and thus
>> fail.
> 
> newLISP
> 
> (define (cartesian-product lists)
>    (if (null? lists)
>      '(())
>      (let (subproduct (cartesian-product (rest lists)))
>        (apply append
>          (map
>            (fn (x) (map (fn (xs) (cons x xs)) subproduct))
>            (first lists))))))
> 
> (define (good? xs)
>    (for-all
>      (fn (pair) (starts-with (pair 1) ((pair 0) -1)))
>      (map list (0 -1 xs) (rest xs))))
> 
> (filter good?
>    (cartesian-product
>      '(("preconize" "cozy" "Lilliputian")
>        ("climb" "nub" "snob" "end" "yet")
>        ("however" "by" "but" "so" "tot")
>        ("the" "that" "a" "tack" "of")
>        ("frog" "elephant" "thing")
>        ("walked" "treaded" "grows")
>        ("slowly" "quickly")
>        ("yank" "can" "you" "choose")
>        ("won't" "understand"))))
> 
> (("cozy" "yet" "tot" "that" "thing" "grows" "slowly" "you"
>    "understand")
>   ("Lilliputian" "nub" "but" "that" "thing" "grows" "slowly"
>    "you" "understand"))


Did you avoid using  Scheme  because it's bad for this
type of string  manipulation?

        -----  e.g.  in Python the last char of string is just String[-1]



       >>> May 12, 2019 — newLISP is a general purpose scripting 
language for developing web applications and programs in general in the 
domains of artificial ...