Math::BigSym looks very interesting - I will have to spend some time
looking at it so I can fully appreciate what you are doing.
You are right that there is no support for multiplication of logarithms as
yet in Math::Algebra::Symbols - I will add it to the to-do list.
I would urge that if x and y are known numerically in $x**$y that you use
the numeric capabilities of Math::GMPq or BigRat or similar.
Math::Algebra::Symbols (MAS) comes into play when you have an expression
like: *$x**4/$x**2 *which it will simplify to* $x**2* which can then be
evaluated much more reliably - or better yet fed into other symbolic
expressions.
As an extreme example, MAS will agree that cos² 𝝷 + sin² 𝝷 == 1, whereas
if you do this sort of thing numerically you tend to get things like
1+1e-63 == 1 which is uncertain - hence the value of symbolic computation
in simplifying things before they are evaluated numerically.
Please let me know if you have any other questions - your project looks to
be a very interesting one and I will be happy to provide some help if that
would be useful to you.
Thanks,
Phil <
http://www.appaapps.com/cgi-bin/DashBoard/allStarts.pl>
Philip R Brenan <
http://www.appaapps.com/cgi-bin/DashBoard/allStarts.pl>
On Fri, May 13, 2016 at 6:51 PM, Trizen Daniel via RT <
bug-Math-Algebra-Symbols@rt.cpan.org> wrote:
Show quoted text> Queue: Math-Algebra-Symbols
> Ticket <URL:
https://rt.cpan.org/Ticket/Display.html?id=114363 >
>
> On Fri May 13 13:34:18 2016, philiprbrenan@gmail.com wrote:
> > Hi Trinzen:
> >
> > Thank you for your excellent bug report. Please try:
> >
> > my ($x) = symbols(qw(x));
> >
> > print 1/$x**4;
> >
> > print $x**-4;
> >
> > Please remember we are doing symbolic algebra here not numeric
> > computation. To actually evaluate a specific expression I believe you
> can
> > do something like:
> >
> > my $y = 1/$x**4;
> >
> > print $y->evaluate(x=>3);
> >
> > I.e first create the desired symbolic expression and then evaluate it
> for a
> > specific value of x.
> >
> > You might find find that *say* is easier to use than *print*.
> >
> > Please let me know if I can help you further?
> >
> >
> > Thanks,
> >
> > Phil <
http://www.appaapps.com/cgi-bin/DashBoard/allStarts.pl>
> >
> > Philip R Brenan <
http://www.appaapps.com/cgi-bin/DashBoard/allStarts.pl>
> >
> > On Fri, May 13, 2016 at 6:25 PM, Trizen Daniel via RT <
> > bug-Math-Algebra-Symbols@rt.cpan.org> wrote:
> >
> > > Fri May 13 13:25:33 2016: Request 114363 was acted upon.
> > > Transaction: Ticket created by TRIZEN
> > > Queue: Math-Algebra-Symbols
> > > Subject: Infinite loop with negative powers
> > > Broken in: (no value)
> > > Severity: (no value)
> > > Owner: Nobody
> > > Requestors: TRIZEN@cpan.org
> > > Status: new
> > > Ticket <URL:
https://rt.cpan.org/Ticket/Display.html?id=114363 >
> > >
> > >
> > > Considering the following code:
> > >
> > > #==BEGIN-CODE==#
> > >
> > > use Math::Algebra::Symbols;
> > >
> > > my $x = symbols("3");
> > > my $y = symbols("-4");
> > >
> > > print $x**$y;
> > >
> > > #==END-CODE==#
> > >
> > > Math::Algebra::Symbols gets stuck in an infinite loop and eats all the
> > > available system memory.
> > >
>
>
> Thanks for your quick reply.
>
> To be safe, I ended up using "exp(log(x) * y)" to mean "x**y", but I think
> this is a bug that can be easily fixed, by checking the sign of "y" before
> performing the actual computation.
>
> I found this bug during the creation and testing of the Math::BigSym
> module, which is a wrapper around Math::GMPq and Math::Algebra::Symbols.
>
> However, using logarithms with Math::Algebra::Symbols seems to be quite
> dangerous, as there is no support for multiplication of logarithms. Or is
> this something that is planed to be added somewhere in the near future?
> That would be very awesome.
>
> Thank you very much.
>
