On Dec 6, 7:34 pm, Anton81 <gerenu...@googlemail.com> wrote: > I do some linear algebra and whenever the prefactor of a vector turns > out to be zero, I want to remove it.
Hmm. Comparing against zero is something of a special case. So you'd almost certainly be doing an 'if abs(x) < tol: ...' check, but the question is what value to use for tol, and that (again) depends on what you're doing. Perhaps 'tol' could be something like 'eps * scale', where 'eps' is an indication of the size of relative error you're prepared to admit (eps = 1e-12 might be reasonable; to allow for rounding errors, it should be something comfortably larger than the machine epsilon sys.float_info.epsilon, which is likely to be around 2e-16 for a typical machine), and 'scale' is something closely related to the scale of your problem: in your example, perhaps scale could be the largest of all the prefactors you have, or some sort of average of all the prefactors. There's really no one-size-fits-all easy answer here. > I'd like to keep the system comfortable. So basically I should write a > new class for numbers that has it's own __eq__ operator? That's probably not a good idea, for the reasons that Carl Banks already enumerated. Mark -- http://mail.python.org/mailman/listinfo/python-list
