On Wed, Feb 13, 2013 at 10:43 AM, Pedro Giffuni <p...@apache.org> wrote: > FWIW; > > > ----- Messaggio originale ----- >> Da: Andrew Douglas Pitonyak > >>> >>> Of course, had I implemented quaternion math using Boost, no one would be >> complaining. :-P >>> >>> Pedro. >>> >>> [1] http://bikeshed.org >> Do it, do it, do it; PLEEEEEEEEEEEEEESSSSSSSSSSEEEEEEE..... :-) >> >> Quaternions are cool. >> > > I think it is easy, and likely a nice exercise for someone wanting to start > AOO development. Perhaps GSoC material. > >> After that, how about interval arithmetic! I think that is even more fun! >> > > I don't know about that, sorry ;). >
It could be used as a form of sensitivity analysis. A value in a spreadsheet might be a known value, like a sales tax rate, that is certain. But you also might have other values that are measurements with measurement error, or estimates with confidence levels. If you treat these unknowns as intervals then you can get some interesting results: http://en.wikipedia.org/wiki/Interval_arithmetic Even better is to allow cells to have an associated distribution, e.g., normal with given mean and variance, uniform within a given interval, etc. If you also have the ability to define covariances between the variables then you can do a monte carlo simulation to determine the distribution of the result cells. Very powerful technique. Today, conceptually at least, a spreadsheet commonly has these different "layers" that are associated with each cell: 1) Contents, e.g., a number, string, formula, blank. 2) A value, e.g., the evaluation of the formula, or the value of a literal. 3) A format, e.g., currency 2 decimal places 4) A style, e.g., green background, bold text There is a lot we could do if we made it easy for extension authors to add more "layers" to a spreadsheet. For example, a layer for dimensions and units (meters, inches, foot-pounds/second, etc. ) would allow error checking for incorrectly mixing dimensions as well automatically converting units. So adding a cell containing seconds to one containing meters would be flagged as an error. But adding meters and feet might be permitted and a conversion factor automatically made. You could also imagine a layer for probability distribution, etc. There is no need for the core of Calc to understand the custom layers other than to respect them during editing operations, e.g., a cut and paste operation brings along contents, format, style, as well as any custom layer metadata. >From the ODF perspective, this could all be done using ODF 1.2's RDF metadata capabilities. -Rob > Pedro. >
