# Re: [mathonweb] reminder: meetings this week

From: Volker Sorge <volker.sorge@gmail.com>
Date: Mon, 10 Sep 2018 20:51:20 +0100
Message-ID: <CAE5-06T82xiZzgk-CGjSj9FrhqzeQPv0x+7_CDxEDC8XUi-pXQ@mail.gmail.com>
To: Neil Soiffer <soiffer@alum.mit.edu>
Cc: Peter Krautzberger <peter@krautzource.com>, mathonweb <public-mathonwebpages@w3.org>
```I am confused; I don't understand your point. I was explicitly referring to
classical logic.
Of course you can define a precedence order. Programming languages often do
following Boolean algebra habits, so do often authors of logic text books.
But even then the order between and/or can depend on the author.

On Mon, 10 Sep 2018 at 19:10, Neil Soiffer <soiffer@alum.mit.edu> wrote:

> I disagree about there not being an accepted precedence for *and* vs *or*.
> The precedence in programming languages that I know all have *and *with a
> higher precedence than *or*. In MathML, the default operator table does
> so also. The other notation used for logical and/or is  ·/+ (as in a ·b + c
> or ab+c) and these again use the convention that the "times" operator has a
> higher precedence than "plus" for and/or.
>
> It may be that some books/articles do it the other way around, but I'd
> like to see some examples proving me wrong. Or if they are considered equal
> precedence, again, I'd like to see some examples where this is true (as
> opposed to just using parens to make it clearer).
>
>     Neil
>
>
> On Mon, Sep 10, 2018 at 10:55 AM, Volker Sorge <volker.sorge@gmail.com>
> wrote:
>
>> There is no precedence order for logical and/or ∧/∨.
>> Precedence in classical logic is: negation over conjunction/disjunction
>> over (material) implication over equivalence.
>> You always need to disambiguate order of and/or.
>> Volker
>>
>> On Mon, 10 Sep 2018 at 18:33, Neil Soiffer <soiffer@alum.mit.edu> wrote:
>>
>>> Apologies for missing the meeting today -- I don't seem to have the
>>> meetings properly entered into my calendar and due to the time difference,
>>> I don't see Peter's reminders until after I start work.
>>>
>>> I have a question about what someone wrote on the Wiki:
>>>
>>>>      a∧b∨c it is not clear the order precedence. Usually ∧ has
>>>> precedence over ∨, but not always.
>>>>
>>>
>>> Can someone clarify (on the wiki) *when* it the normal precedence
>>> doesn't hold. What surprised me when I first looked into notations and
>>> precedence (20 years ago -- yikes!) was that although a symbols might have
>>> many different meanings, the precedence relationships it has didn't seem to
>>> change. I attributed that to people trying to avoid confusion when using
>>> familiar notation for new functionality. Having '∨' have a different
>>> precedence relative to '∧' in some cases seems very strange to me. But
>>> mathematicians do strange things at times (especially logicians ;-).
>>>
>>>     Neil
>>>
>>>
>>>
>>> www.avg.com
>>>
>>> On Mon, Sep 10, 2018 at 12:36 AM, Peter Krautzberger <
>>> peter@krautzource.com> wrote:
>>>
>>>> Hi everyone,
>>>>
>>>> Just a quick reminder for the CG meetings this week.
>>>>
>>>> - a11y TF, Monday, Sept 10, 11am Eastern
>>>> - css TF, Monday, Sept 10, 12pm Eastern
>>>> - no CG meeting this week
>>>>
>>>> Best,
>>>> Peter.
>>>>
>>>
>>>
>
```
Received on Monday, 10 September 2018 19:51:56 UTC

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