On Thu, Dec 10, 2009 at 1:33 PM, kcrisman <kcris...@gmail.com> wrote:
>
>
> On Dec 10, 2:49 pm, William Stein <wst...@gmail.com> wrote:
>> On Thu, Dec 10, 2009 at 10:32 AM, kcrisman <kcris...@gmail.com> wrote:
>>
>> >> At this point, I'm just throwing some remarks out, not saying that we
>> >> should
>> >> do anything in particular.
>>
>> >> I'm curious -- who multiplies equalities by a scalar *except* high school
>> >> students or college students taking entry level college algebra classes?
>>
>> > Or those in calculus or LP classes who need them to find solution sets
>> > to various things. But yes.
>>
>> So we should make the semantics be aimed at such people.
>
> But, although
> x<y
> -x>-y
> what would we do for
> a*x??a*y
> situation? I think this was alluded to above - there isn't an answer,
> per se. That doesn't mean we couldn't check for the 'right' answer if
> 'a=something numeric' or even if 'a is assumed to be pos. or neg. in
> assumptions()'. But it's not clear what to do in that case, and we
> don't want to cause things to happen that are simply wrong. What does
> Maple do in the symbolic case (the Mma answer, though cryptic, at
> least is consistent)?
Here is what Maple does:
flat:release_notes wstein$ maple
|\^/| Maple 13 (APPLE UNIVERSAL OSX)
._|\| |/|_. Copyright (c) Maplesoft, a division of Waterloo Maple Inc. 2009
\ MAPLE / All rights reserved. Maple is a trademark of
<____ ____> Waterloo Maple Inc.
| Type ? for help.
> f := x < y;
f := x < y
> f*(-3)
> ;
-3 y < -3 x
> f*z;
*(x < y, z)
> f*a;
*(x < y, a)
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