On Dec 9, 2008, at 7:38 PM, William Stein wrote:
> > This is not the answer. Look at this example: > > sage: srange(0,1.1,0.1,include_endpoint=True) > [0.000000000000000, > 0.100000000000000, > 0.200000000000000, > 0.300000000000000, > 0.400000000000000, > 0.500000000000000, > 0.600000000000000, > 0.700000000000000, > 0.800000000000000, > 0.900000000000000, > 1.00000000000000, > 1.10000000000000, > 1.20000000000000] > > That's not right no matter what. The documentation says: > " Return list of numbers a, a+step, ..., a+k*step, > where a+k*step < b and a+(k+1)*step > b." > where a,b are the first two inputs. > > Thus the implementation of srange is simply buggy because the person > (me!) who implemented didn't take proper care of how floating point > numbers behave. > I ran across this in some timestepping code I wrote for a ODE solver for systems of second order ODEs. The general trick I used is to set the first n-1 terms based upon the formula and set the final one to the endpoint. It means that the final one may be shorter, but that way it always ends at the set endpoint. Cheers, Tim. --- Tim Lahey PhD Candidate, Systems Design Engineering University of Waterloo http://www.linkedin.com/in/timlahey --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
