integrate returns undefined .. Bug in zero denominator?

The result from solve is clearly not a solution.  But your proposed solution
is not right because
x= y+n*%pi,  n integer and nonzero IS a solution.

The point I was trying to make is that you cannot say it is ok to be 
just a little slipshod because you yourself
will be aware of something  (like a denominator being zero).

There are enough subtle problems with detecting zero that you can't always
do it.
But that's not a positive feature.

Once you are aware of a "feature" that is really a bug, you can construct
many erroneous
results, as Vladimir Bondarenko does, on sci.math.symbolic.

RJF
 

> -----Original Message-----
> From: Richard Hennessy [mailto:rvh2007 at comcast.net] 
> Sent: Wednesday, September 10, 2008 8:23 AM
> To: fateman at EECS.Berkeley.EDU
> Cc: maxima at math.utexas.edu
> Subject: Re: [Maxima] integrate returns undefined
> 
> Rich,
> 
> Automatic taking of limits is not always the answer for many people. 
> Personnally I would like this feature
> (%i1) solve (sin(x-y)/(x-y)=0,x);
> (%o1) []
> 
> since I think a "solution" that makes the demominator zero is 
> never "right".
> 
> Rich
> 
> 
> ----- Original Message ----- 
> From: "Richard Fateman" <fateman at cs.berkeley.edu>
> To: "'Richard Hennessy'" <rvh2007 at comcast.net>
> Cc: <maxima at math.utexas.edu>
> Sent: Wednesday, September 10, 2008 11:04 AM
> Subject: RE: [Maxima] integrate returns undefined
> 
> 
> > Your saying that something is not a bug does not mean 
> everyone will agree
> > with you.
> > Or even that it will result in non-buggy results.  Many 
> "bugs" reported on
> > sci.math.symbolic
> > by one writer as bugs in "integrate"  in Maple, are bugs in 
> > simplification,
> > sometimes
> > just like this "obvious" but sometimes wrong feature.
> >
> > In particular, you may not need reminding about a=0 in this 
> case, but what
> > about
> > in other cases, where Maxima just goes ahead without you... e.g.
> > solve (sin(x-y)/(x-y)=0,x)
> >
> > returns x=y;
> > but this is not a solution, which can be seen either by direct 
> > substitution
> > or
> > taking a limit.
> >
> > RJF
> >
> >
> >
> >
> >
> >
> >
> >> -----Original Message-----
> >> From: Richard Hennessy [mailto:rvh2007 at comcast.net]
> >> Sent: Wednesday, September 10, 2008 7:26 AM
> >> To: fateman at EECS.Berkeley.EDU; 'John Pye'; maxima at math.utexas.edu
> >> Cc: 'Edwin Woollett'
> >> Subject: Re: [Maxima] integrate returns undefined
> >>
> >> This is not a bug, this simplifies to 1
> >>
> >> a/a -> 1
> >>
> >> with no assumptions made.  I have noticed that in general
> >> radcan(expr1/expr1) simplifies to 1 and Maxima never says
> >> except when expr1
> >> = 0.  Which I find useful since I know about the possibility
> >> that expr1
> >> could be zero but I don't really need to be reminded of 
> this case.  I
> >> definitely would not want to be asked is expr1 = zero all the
> >> sime when
> >> cancelling terms.  That would be annoying.
> >>
> >> Rich
> >>
> >>
> >> ----- Original Message ----- 
> >> From: "Richard Fateman" <fateman at cs.berkeley.edu>
> >> To: "'John Pye'" <john.pye at anu.edu.au>; <maxima at math.utexas.edu>
> >> Cc: "'Edwin Woollett'" <woollett at charter.net>
> >> Sent: Tuesday, September 09, 2008 11:56 PM
> >> Subject: Re: [Maxima] integrate returns undefined
> >>
> >>
> >> > Not so clear a bug.
> >> > (n-m)/(n-m) simplifies to 1.
> >> > But if you know n=m, then you have 0/0.  So is it a bug if
> >> (n-m)/(n-m) -->
> >> > 1?
> >> >
> >> > Answer: maybe. But not clear :)
> >> >
> >> > RJF
> >> >
> >> >
> >> >> -----Original Message-----
> >> >> From: maxima-bounces at math.utexas.edu
> >> >> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of John Pye
> >> >> Sent: Tuesday, September 09, 2008 6:47 PM
> >> >> To: maxima at math.utexas.edu
> >> >> Cc: Edwin Woollett
> >> >> Subject: Re: [Maxima] integrate returns undefined
> >> >>
> >> >> I can confirm that behaviour; it looks like a clear bug to me.
> >> >>
> >> >> Cheers
> >> >> JP
> >> >>
> >> >> Edwin Woollett wrote:
> >> >> > integrate(..) returns undefined when it
> >> >> > should know the answer.
> >> >> >
> >> >> > (%i1) declare( [ m, n ], integer )$
> >> >> > (%i2) assume ( m > 0,  n > 0 )$
> >> >> > (%i3) integrate( cos(m*x)^2, x, 0, 2*%pi );
> >> >> > (%o3)                                 %pi
> >> >> > (%i4) integrate( cos(m*x)*cos(n*x), x, 0, 2*%pi  );
> >> >> > Is  n - m  positive, negative, or zero?
> >> >> >
> >> >> > zero;
> >> >> > (%o4)                              undefined
> >> >> >
> >> >> > Is this a known bug?
> >> >>
> >> >> _______________________________________________
> >> >> Maxima mailing list
> >> >> Maxima at math.utexas.edu
> >> >> http://www.math.utexas.edu/mailman/listinfo/maxima
> >> >>
> >> >
> >> > _______________________________________________
> >> > Maxima mailing list
> >> > Maxima at math.utexas.edu
> >> > http://www.math.utexas.edu/mailman/listinfo/maxima
> >>
> >>
> > 
> 
>