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Re: Undefined behaviour, was: for or against equality

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On Tue, 11 Jan 2022 16:55:54 -0000 (UTC), Kaz Kylheku
<480-992-1380@kylheku.com> wrote:

>On 2022-01-08, Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>>>Undefined behaviour, as far as language standards are concerned, are
>>>omnipresent in programming - for all languages.
>>
>> Please prove this astounding assertion.  My impression is that managed
>> languages define everything, at least to some extent, and leave
>> nothing undefined.  If they allowed nasal demons, the appeal of
>> managed languages would evaporate instantly.
>
>The Lisp-like programming language Scheme has unspecified order of
>argument evaluation. And you can stuff side effects into argument
>expressions, like in C.

In Scheme the order of evaluation for let expressions similarly is
unspecified.

There is at least one Scheme which deliberately randomizes the order
of function argument and let evaluation.  And there are parallel
Schemes which evaluate function arguments and lets in parallel.


>Its built-in imperative have undefined return values.
>
>ANSI Common Lisp leaves the effects undefined of modifying literals,
>just like C.  ANSI Lisp code that perpetrates some kind of error is
>safe only if compiled in safe mode; if you compile with reduced safety,
>e.g. (declare (optimize (safety 0))), then error become undefined
>behavior, including type errors. If you declare that some quantity is
>a fixnum integer, and request safety 0 speed 3, and then it turns
>out that it's other than an integer, woe to that code.
>However, in these cases you're invoking the safety escape hatch;
>it's not like C where you are shackled by chains of undefined behavior
>which make themselves felt every time you squirm.

And Lisp's optimization settings can be changed per function or per
compilation unit as well as globally.  ["declaim" vs "declare"]

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Re: for or against equality, was Why are ambiguous grammars usually a bad idea? Martin Ward <martin@gkc.org.uk> - 2022-01-05 10:25 +0000
  Re: for or against equality, was Why are ambiguous grammars usually a bad idea? David Brown <david.brown@hesbynett.no> - 2022-01-06 09:11 +0100
    Re: what is defined, was for or against equality Thomas Koenig <tkoenig@netcologne.de> - 2022-01-06 16:43 +0000
      Re: what is defined, was for or against equality David Brown <david.brown@hesbynett.no> - 2022-01-07 12:06 +0100
      Re: what is defined, was for or against equality Spiros Bousbouras <spibou@gmail.com> - 2022-01-07 13:21 +0000
        Re: what is defined, was for or against equality Thomas Koenig <tkoenig@netcologne.de> - 2022-01-08 09:31 +0000
          Re: what is defined, was for or against equality Spiros Bousbouras <spibou@gmail.com> - 2022-01-08 22:28 +0000
            Re: what is defined, was for or against equality Thomas Koenig <tkoenig@netcologne.de> - 2022-01-09 00:09 +0000
              Re: what is defined, was for or against equality Spiros Bousbouras <spibou@gmail.com> - 2022-01-09 21:30 +0000
          Re: what is defined, was for or against equality David Brown <david.brown@hesbynett.no> - 2022-01-09 23:00 +0100
            Re: what is defined, was for or against equality Thomas Koenig <tkoenig@netcologne.de> - 2022-01-10 12:04 +0000
              Re: what is defined, was for or against equality David Brown <david.brown@hesbynett.no> - 2022-01-11 18:16 +0100
                Re: what is defined, was for or against equality Kaz Kylheku <480-992-1380@kylheku.com> - 2022-01-11 19:19 +0000
                Re: what is defined, was for or against equality gah4 <gah4@u.washington.edu> - 2022-01-11 14:18 -0800
                Re: what is defined, was for or against equality Thomas Koenig <tkoenig@netcologne.de> - 2022-01-12 19:02 +0000
                Re: what is defined, was for or against equality David Brown <david.brown@hesbynett.no> - 2022-01-13 08:24 +0100
                Re: what is defined, was for or against equality Thomas Koenig <tkoenig@netcologne.de> - 2022-01-13 11:17 +0000
          Re: what is defined, was for or against equality gah4 <gah4@u.washington.edu> - 2022-01-10 16:58 -0800
    Re: for or against equality, was Why are ambiguous grammars usually a bad idea? Robert Prins <robert@prino.org> - 2022-01-06 19:07 +0000
    Undefined behaviour, was: for or against equality Martin Ward <martin@gkc.org.uk> - 2022-01-07 14:02 +0000
      Re: Undefined behaviour, was: for or against equality Spiros Bousbouras <spibou@gmail.com> - 2022-01-08 03:41 +0000
    Re: Undefined behaviour, was: for or against equality David Brown <david.brown@hesbynett.no> - 2022-01-07 15:56 +0100
      Re: Undefined behaviour, was: for or against equality anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2022-01-08 17:52 +0000
        Re: Undefined behaviour, was: for or against equality David Brown <david.brown@hesbynett.no> - 2022-01-09 23:53 +0100
        Re: Undefined behaviour, was: for or against equality Kaz Kylheku <480-992-1380@kylheku.com> - 2022-01-11 16:55 +0000
          Re: Undefined behaviour, was: for or against equality George Neuner <gneuner2@comcast.net> - 2022-01-11 22:01 -0500

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