I agree w/ Chuck - I'd consider what Tim describes is happening a "bug".
DG Charles R Harris wrote: > > > On 2/21/07, *Timothy Hochberg* <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > > > On 2/21/07, *Charles R Harris* < [EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > > > On 2/21/07, *Robert Kern* < [EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > Christopher Barker wrote: > > Robert Kern wrote: > >> Christopher Barker wrote: > >>> I wonder if there are any C math libs that do a better > job than you'd > >>> expect from standard FP? (short of unlimited precision > ones) > >> With respect to π and the zeros of sin() and cos()? Not > really. > > > <snip> > > Well, you can always use long double if it is implemented > on your platform. You > will have to construct a value for π yourself, though. I'm > afraid that we don't > really make that easy. > > -- > > > pi = 3. 1415926535 8979323846 2643383279 5028841971 6939937510 > 5820974944 5923078164 0628620899 8628034825 3421170679 > 8214808651 *... > > * > I dont know what that looks like when converted to long > double. Lessee, > > In [1]: import numpy > > In [2]: pi = > numpy.float128(3.1415926535897932384626433832795028841971) > > > I think this is where you go wrong. Your string of digits is first > a python float and *then* is converted to a long double. In the > intermediate stage it gets truncated and you don't get the > precision back. > > > True. But there is missing functionality here. > > In [4]: pi = numpy.float128('3.1415926535897932384626433832795028841971') > --------------------------------------------------------------------------- > > exceptions.TypeError Traceback (most > recent call last) > > /home/charris/workspace/microsat/daemon/<ipython console> > > TypeError: a float is required > > It's somewhat pointless to have a data type that you can't properly > initialize. I think the string value should work, it works for python > types. > > Chuck > > ------------------------------------------------------------------------ > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion > -- ERD/ORR/NOS/NOAA <http://response.restoration.noaa.gov/emergencyresponse/> _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
