On Thu, Nov 5, 2009 at 10:31 AM, Michael Orlitzky <[email protected]> wrote: > > Jason Grout wrote: >> >> Interesting. I consider a brief discussion of numerical instability an >> essential feature of a first-semester linear algebra course. These >> students will most likely be using numerical linear algebra in real-life >> problems, and it will help a *lot* to at least have had exposure to >> realize that the computer may not be all-knowing and all-powerful like >> they had supposed. >> >> That said, I almost always define my matrices over QQ if I'm trying to >> mirror a student's work that they've done by hand. > > I don't mean to beat a dead horse, but this problem isn't something that > can be overcome by teaching numerical (in)stability. I understand the > floating point issues well enough; my question was never, > > Why does this happen with matrices of floats? > > but rather, > > If we know matrices of floats return junk, why does SAGE parse my > (matrix) inputs as floats? > > The answer "because you told it to," isn't very satisfying, because it > relies on my knowing the nowhere-documented[1] internal detail that > inputs containing decimals will be stored as floating point numbers, > even in cases (e.g. matrices) where the outcome will be less than desirable.
So we document it. Problem solved. William --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
