id summary reporter owner description type status priority milestone component resolution keywords cc merged author reviewer upstream work_issues branch commit dependencies stopgaps
10133 Make sin(0), log(1) and similar expressions return Sage integers, not Python ints kcrisman burcin "From [http://groups.google.com/group/sage-devel/browse_thread/thread/cceabb7271022b1c/944c94af910269a0 this thread]:
{{{
> > sage: type(log(1))
> >
> > sage: log(1).n()
> > ---------------------------------------------------------------------------
> > AttributeError: 'int' object has no attribute 'n'
> > sage: Integer(log(1)).n()
> > 0.000000000000000
> > sage: a = Integer(1)
> > sage: a.log()
> > 0
> > sage: type(a.log())
> >
> > sage: from sage.functions.log import function_log
> > sage: function_log(Integer(1))
> > 0
> > sage: type(function_log(Integer(1)))
> >
>
> > Is there any way to get around this in the code, or are we pretty much
> > stuck with this because of how GinacFunctions work? I'm not 100% sure
> > this is a bug in log; maybe instead we should extend int so that
>
> This is a bug in the log() function, and any other function which
> returns exact values like 0 or 1. We already work around most cases,
> see lines 720-722 and 736-761 of sage/symbolic/function.pyx.
>
> The correct fix is to change the corresponding pynac functions to
> coerce the exact value to the parent of the argument before returning
> it. For example, all the lines ""return _ex1;"" or ""return _ex0;"" in
>
> http://pynac.sagemath.org/hg/file/b233d9dadcfa/ginac/inifcns_trans.cpp
>
> has to be changed this way.
>
Yup, I see what you are talking about - e.g.
if (x.is_equal(_ex1)) // log(1) -> 0
return _ex0;
Although it might be nice to stay relatively close to Ginac and fix such things on the Sage level if that's not really bad.
}}}
This ticket's goal is to implement one of these solutions (that is, catch this in function.pyx or in Pynac).
We might as well also deal with {{{sin(0), tan(0), sin(pi)}}} from #10972 here as well, otherwise that really wasn't a duplicate." defect closed major sage-6.4 symbolics fixed type coercion symbolic eviatarbach Jeroen Demeyer Ralf Stephan N/A c8c26e1ca6195841b5bd1bb900a33eef3bb30b60 #17130