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Re: sobre loops em common lisp

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From Patricia Ferreira <pferreira@example.com>
Newsgroups pt.comp.programacao
Subject Re: sobre loops em common lisp
Date Tue, 05 Mar 2024 20:07:02 -0300
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Patricia Ferreira <pferreira@example.com> writes:

> Patricia Ferreira <pferreira@example.com> writes:
>
> [...]
>
>> Eis meu segundo.  Gere um nome (de arquivo) aleatório e tente usá-lo.
>> Se calhar de alguém já tê-lo escolhido, tente de novo (com outro nome).
>> Feito isso, retorne-nos esse nome sortudo e pra que a gente possa
>> renomeá-lo pro seu nome final---accounts.lisp.
>>
>> (defun write-accounts ()
>>   (let ((name
>>           (loop 
>>             (let* ((tmp (random-string 10))
>>                    (name (format nil "~a.tmp" tmp)))
>>               (when 
>>                   (ignore-errors 
>>                    (with-open-file 
>>                        (s name
>>                           :direction :output
>>                           :if-exists :error
>>                           :if-does-not-exist :create)
>>                      (write *accounts* :stream s)))
>>                 (return name))))))
>>     (rename-file name "accounts.lisp")
>>     *accounts*))
>>
>> Tecnicamente temos um problema com esse procedimento.  Se o rename-file
>> não obtiver sucesso, nem vamos saber.
>
> Não sei o que fazer se o rename não ocorrer, mas ficamos a versão final:
>
> (defun write-accounts ()
>   (let ((name
>           (loop 
>             (let* ((tmp (random-string 10))
>                    (name (format nil "~a.tmp" tmp)))
>               (when 
>                   (ignore-errors 
>                    (with-open-file 
>                        (s name
>                           :direction :output
>                           :if-exists :error
>                           :if-does-not-exist :create)
>                      (write *accounts* :stream s)))
>                 (return name))))))
>     (if (ignore-errors (rename-file name "accounts.lisp"))
>         *accounts*
>         (format t "could not rename ~a to account.lisp" name))))

Lol.  Não é isso que quero, não.  O que quero é:

(defun write-accounts ()
  (let ((name
          (loop 
            (let* ((tmp (random-string 10))
                   (name (format nil "~a.tmp" tmp)))
              (when 
                  (ignore-errors 
                   (with-open-file 
                       (s name
                          :direction :output
                          :if-exists :error
                          :if-does-not-exist :create)
                     (write *accounts* :stream s)))
                (return name))))))
    (if (ignore-errors (rename-file name "accounts.lisp"))
        *accounts*
        (format nil "could not rename ~a to accounts.lisp" name))))

PACKAGE> (write-accounts)
"could not rename wqjjpdlifi.tmp to accounts.lisp"

Agora sim.

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Thread

sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-02-27 21:48 -0300
  Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-02-28 18:25 +0000
    Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-02-28 21:49 -0300
      Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-02-29 10:15 +0000
        Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-03 22:49 -0300
          Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-03-04 07:55 +0000
            Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-04 14:37 -0300
              Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-03-04 19:49 +0000
                Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-04 21:46 -0300
                Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-03-05 09:03 +0000
                Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-05 17:21 -0300
                Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-03-06 08:56 +0000
                Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-08 17:16 -0300
                Re: sobre loops em common lisp Daniel Cerqueira <dan.list@lispclub.com> - 2024-03-08 21:11 +0000
                Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-08 18:38 -0300
      Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-05 17:23 -0300
        Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-05 19:50 -0300
          Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-05 20:05 -0300
            Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-05 20:07 -0300
              Re: sobre loops em common lisp Patricia Ferreira <pferreira@example.com> - 2024-03-08 17:12 -0300

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