The floating point "fields" in Sage (RR or RDF) can represent both infinity and NaN. So you'll have to check separately if this is the case. Note that "x in RR" checks that x can be represented in RR.
On Saturday, April 28, 2012 7:38:44 AM UTC-4, Duc Trung Ha wrote: > > Hola, > > I'm stuck at the problem of determinating whether a given expression is > known to be real number or not. > > > > > So far, I've been testing this either > with > > > expr.is_real() > > > > or > > > > expr in > RR > > > > succesfully. > > Now, if I give Sage this expression of real number: > -1/12*pi + 1/12*sqrt(16*pi + pi^2 + 256) + 4/3 > the following results will occur: > > http://aleph.sagemath.org/?z=eJxLVLBV0DXUNzTSKshU0FYAs4oLi0o0DM0gIgWZcUZAysjUTBNImegbc3EVFGXmlSgk6mUWxxelJuZoaMKFFDLzFIKCAHCUFik%3D > > On the other hand, non-real value below: > arccos(2) > would produce the very same results, though it should give opposite > results for at least 1 test: > > http://aleph.sagemath.org/?c=a+%3D+arccos%282%29%0A%0Aprint+a.is_real%28%29%0A%0Aprint+a+in+RR > > Is there any other/standard way to test membership to real numbers? > > Is this a bug or is it covered somewhere else? > Duc Trung Ha > Sage Version 4.8, Release Date: 2012-01-20 > Intel(R) Core(TM) i5-2410M CPU @ 2.30GHz > Kubuntu 12.04 > -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
