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Re: Operator precedence

From Janis Papanagnou <janis_papanagnou+ng@hotmail.com>
Newsgroups comp.lang.awk
Subject Re: Operator precedence
Date 2024-05-25 23:31 +0200
Organization A noiseless patient Spider
Message-ID <v2tlcc$320fr$1@dont-email.me> (permalink)
References (1 earlier) <20240523092856.646@kylheku.com> <87sey8movv.fsf@axel-reichert.de> <v2okuh$1vrvh$1@dont-email.me> <v2ouo9$2547f$1@dont-email.me> <20240523210755.307@kylheku.com>

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On 24.05.2024 06:32, Kaz Kylheku wrote:
> On 2024-05-24, Janis Papanagnou <janis_papanagnou+ng@hotmail.com> wrote:
>> After pondering a bit more I think this is my personal resume...
>>
>> On 24.05.2024 01:53, Janis Papanagnou wrote:
>>> [...]
>>> Moreover, what seams reasonable (to me) is that _unary_ operators
>>> should (typically/always?) bind tighter than _binary_ operators!
>>
>> An example may make things probably more apparent; in the expression
>>
>>     5 * -3 ^ 2
>>
>> it would never occur to me to not consider the "-3" as an entity.
>> Because of the typical inherently tight coupling of unary operators.
>>
>> (Assuming an interpretation of
>>
>>     5 * -(3 ^ 2)
>>
>> would look just wrong to me.)
> 
> That interpretation is required if - 3 ^ 2  is to correspond to:
> 
>     2
>   -3
> 
> Indeed the ^ circumflex is intended to mean "we don't have support
> for superscripts in this notation, but pretend that the 2 is raised up".
> 
> (In TeX/LaTeX, ^ is used for marking up superscripts: x^y.)
> 
> Now in the C grammar, we have multiplication also occuping a
> precedence rung between unary plus/minus and additive expressions.
> 
> Thus -A*B means (-A)*B, whereas X - A*B means X-(A*B).
> 
> In this case it doesn't matter because the unary minus is
> a kind of product. -A can be regarded as a shorthand for (-1)*A.
> 
> More importantly the identity (-A)*B = -(A*B) holds.

So far so good, only it doesn't (IMO) provide a rationale for
exponentiation.

> This creates a problem if we naively wedge exponentiation into
> the grammar, by sticking it into a precedence level above
> multiplication, but below unary.
> 
> The identity does not hold in exponentiation: (-A)**B
> is not -(A**B).

Looks like a non-sequitur to me.

Janis

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Thread

Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-23 16:13 +0200
  Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-23 16:49 +0000
    Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-05-23 19:14 +0200
      Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-24 01:53 +0200
        Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-24 04:41 +0200
          Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-24 04:32 +0000
            Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-05-25 13:34 +0200
              Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-25 23:31 +0200
                Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-26 00:03 +0200
                Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-25 22:26 +0000
                Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-30 06:59 +0200
                Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-05-30 10:24 +0200
                Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-31 17:08 +0200
                Re: Operator precedence Christian Weisgerber <naddy@mips.inka.de> - 2024-05-26 00:37 +0000
                Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-26 02:06 +0000
                Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-30 07:26 +0200
                Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-30 07:06 +0200
                Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-05-30 10:22 +0200
                Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-31 17:16 +0200
            Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-25 23:31 +0200
              Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-26 01:29 +0000
        Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-05-30 10:17 +0200
          Re: Operator precedence Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2024-05-31 17:46 +0200
            Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-06-01 09:11 +0200
      Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-24 03:45 +0000
        Re: Operator precedence Axel Reichert <mail@axel-reichert.de> - 2024-05-25 13:09 +0200
          Re: Operator precedence Kaz Kylheku <643-408-1753@kylheku.com> - 2024-05-25 22:20 +0000

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