Floating point subtraction rounding error (NOT display error)

[Keflavich]

Thanks, I'll have a look at that.  I'm not sure the decimal type is
included in numpy, though, which is what I'm using.  It doesn't show
up in their documentation, at least.

Adam

On Dec 13, 3:39 pm, a... at pythoncraft.com (Aahz) wrote:
> In article <93a9ea9a-00ab-4022-a567-8ba268790... at s12g2000prg.googlegroups.com>,
>
> Keflavich  <keflav... at gmail.com> wrote:
>
> >Hey, I have a bit of code that died on a domain error when doing an
> >arcsin, and apparently it's because floating point subtraction is
> >having problems.  I know about the impossibility of storing floating
> >point numbers precisely, but I was under the impression that the
> >standard used for that last digit would prevent subtraction errors
> >from compounding.
>
> >Is there a simple solution to this problem, or do I need to run some
> >sort of check at every subtraction to make sure that my float does not
> >deviate?  I'm not sure I know even how to do that.
>
> Switch to Decimal module?  Available in 2.4 and later.
> --
> Aahz (a... at pythoncraft.com)           <*>        http://www.pythoncraft.com/
>
> "Typing is cheap.  Thinking is expensive."  --Roy Smith