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Re: Rosetta: Babbage problem

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On 5/9/2017, Robert L. wrote:

> > Charles Babbage, looking ahead to the sorts of problems his
> > Analytical Engine would be able to solve, gave this example:
> > 
> > What is the smallest positive integer whose square ends in the
> > digits 269,696? -- Babbage, letter to Lord Bowden, 1837; see
> > Hollingdale and Tootill, Electronic Computers, second edition,
> > 1970, p. 125.
> > 
> > He thought the answer might be 99,736, whose square is
> > 9,947,269,696; but he couldn't be certain.
> > 
> > Task
> > 
> > The task is to find out if Babbage had the right answer -- and
> > to do so, as far as your language allows it, in code that
> > Babbage himself would have been able to read and understand.
> > 
> > For these purposes, Charles Babbage may be taken to be an
> > intelligent person, familiar with mathematics and with the
> > idea of a computer, who has never programmed--in fact, who has
> > never so much as seen a single line of code.
> > 
> > Motivation
> > 
> > The aim of the task is to write a program that is sufficiently
> > clear and well-documented for such a person to be able to read
> > it and be confident that it does indeed solve the specified
> > problem.
> 
> 
> (use srfi-121)
> 
> ;; Create function that accepts a number and returns
> ;; true if, only if, it satisfies the requirements.
> (define (good? n) (equal? 269696 (modulo (* n n) 1000000)))
> 
> ;; A generator for the natural numbers (1,2,3,4 ...).
> ;; Each time it is called, it yields the next number.
> (define generate-naturals (make-range-generator 1))
> 
> (generator-find good? generate-naturals)
> 
>  ===>
> 25264
> 
> -----
> 
> (use lazy-lists)
> 
> (define (good? n) (equal? 269696 (modulo (* n n) 1000000)))
> 
> (First (Filter good? (Cardinals)))
> 
>  ===>
> 25264
> 
> 
> In Forth?

(let go ((i 0)) (if (= 269696 (modulo (* i i) 1000000)) i (go (+ 1 i))))
 ===>
25264

-- 
[H]e was prosecuted ... for "denying" the gas chambers and the six million
figure....  [A] Swiss court sentenced him to 15 months imprisonment....  Rather
than serve the sentence, ... Graf went into exile.  In 2001 he married a
Russian historian in Moscow.  www.revisionists.com/revisionists/graf.html

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Rosetta: Babbage problem "Robert L." <No_spamming@noWhere_7073.org> - 2017-05-09 08:29 +0000
  Re: Rosetta: Babbage problem mhx@iae.nl - 2017-05-09 12:58 -0700
    Re: Rosetta: Babbage problem Paul Rubin <no.email@nospam.invalid> - 2017-05-09 20:43 -0700
      Re: Rosetta: Babbage problem Julian Fondren <julian.fondren@gmail.com> - 2017-05-09 23:43 -0700
        Re: Rosetta: Babbage problem Lars Brinkhoff <lars.spam@nocrew.org> - 2017-05-10 09:06 +0200
          Re: Rosetta: Babbage problem Julian Fondren <julian.fondren@gmail.com> - 2017-05-10 00:27 -0700
            Re: Rosetta: Babbage problem Lars Brinkhoff <lars.spam@nocrew.org> - 2017-05-10 09:32 +0200
          Re: Rosetta: Babbage problem Paul Rubin <no.email@nospam.invalid> - 2017-05-10 00:59 -0700
            Re: Rosetta: Babbage problem Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-10 08:14 -0500
      Re: Rosetta: Babbage problem mhx@iae.nl - 2017-05-10 02:59 -0700
        Re: Rosetta: Babbage problem Bruno Gauthier <bgauthier@free.fr> - 2017-05-15 12:25 +0200
          Re: Rosetta: Babbage problem mhx@iae.nl - 2017-05-15 04:17 -0700
            Re: Rosetta: Babbage problem Bruno Gauthier <bgauthier@free.fr> - 2017-05-15 13:48 +0200
              Re: Rosetta: Babbage problem Julian Fondren <julian.fondren@gmail.com> - 2017-05-15 04:56 -0700
                Re: Rosetta: Babbage problem Bruno Gauthier <bgauthier@free.fr> - 2017-05-15 16:33 +0200
              Re: Rosetta: Babbage problem mhx@iae.nl - 2017-05-15 10:53 -0700
              Re: Rosetta: Babbage problem albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-15 21:39 +0200
  Re: Rosetta: Babbage problem "Robert L." <No_spamming@noWhere_7073.org> - 2017-05-18 09:23 +0000
    Re: Rosetta: Babbage problem "Robert L." <No_spamming@noWhere_7073.org> - 2017-05-18 09:29 +0000

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