# Re: [mathonweb] reminder: meetings this week

From: Neil Soiffer <soiffer@alum.mit.edu>
Date: Mon, 10 Sep 2018 11:10:56 -0700
Message-ID: <CAESRWkCqt8i0D4TbCN1VqaSeHrExB2MuXJwjghYjpkA6qxV-wg@mail.gmail.com>
To: Volker Sorge <volker.sorge@gmail.com>
Cc: Peter Krautzberger <peter@krautzource.com>, mathonweb <public-mathonwebpages@w3.org>
```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 18:11:20 UTC

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