From: "M. Edward (Ed) Borasky" <znmeb@...>
Date: 2006-08-27T11:41:36+09:00
Subject: Re: and and or priority

Matthew Smillie wrote:
> On Aug 26, 2006, at 16:16, David Vallner wrote:
> 
>> Pavel Smerk wrote:
>>> David Vallner wrote:
>>>> Pavel Smerk wrote:
>>>>
>>>>> OMG!
>>>>>
>>>>> Why the and and or operators have the same priority? Unlike && and
>>>>> || and also unlike the most of, or maybe all, other languages and
>>>>> conventions?
>>>>>
>>>>> (Yes, long time spent on that now, who would expect such a
>>>>> curiosity...)
>>>>>
>>>>> Thanks for explanation, if there is any,
>>>>>
>>>>> P.
>>>>>
>>
>> For what it's worth though, since most programmers DO expect
>> mathemathical rules to hold in programming languages, for the sake of
>> consistency, I agree that the and should bind more tightly than or now
>> that that's been brought up.
> 
> Is that actually a mathematical rule, though?  I don't remember as such
> from any math or logic that I know, and poking around through my old
> textbooks made no mention of binding or precedence of logical
> operations; the closest thing being a statement that parentheses are
> required to avoid ambiguity when mixing and and or in one statement, at
> least slightly implying that there is no 'order of operations'.
> 
> If anyone has a reference either way on this, I'd be curious to see it.
> 
> matthew smillie.
> 
> 
My rather dim recollection is that computer jocks forced "and" to bind
tighter than "or" and "not" to bind tighter than "and" just so it *was*
defined. Only in programming (and logic design) do you usually find
Boolean expressions complicated enough for operator precedence to matter. :)

Meanwhile, the logicians pretty much abandoned parentheses for Polish
(prefix) notation. And of course, the computer jocks, not to be outdone,
invented *reverse* Polish notation. :)