On Wed, May 6, 2009 at 1:46 PM, Yann <yannlaiglecha...@gmail.com> wrote: >> In other words, >> sage: RealIntervalField(4)(0, 1) >> 1.? >> prints as the interval [0 .. 2], rather than [-1 .. 1], because IMHO >> it is useful to be able to know that an interval is nonnegative; and >> we do this by always picking the result farther from zero whenever >> there are two possible "correct" printings. (Note that 3.? and 4.? >> would both include the interval [3.00 .. 3.25], so they are both >> correct in that sense.) > > I would agree if it was 4.?1 (even I find something like 4.?±1 easier > to understand) > but without the error explicitely written, I would prefer to do what > is in the docstring: > " In question style (the default), we print the "known correct" > part of the number " > My understanding of this sentence is that we print the digits known > for sure. And if a > number is in the interval [3.00 .. 3.25], this should be 3.? > The design you decision si only relevant IMHO if the error digits are > explicitely written
We definitely don't want to print "the digits known for sure". Consider the interval [0.999999 .. 1.000001], which would print as 1.000000? with the current code (I'm ignoring the fact that the endpoints are not exactly representable in binary). With printing "the digits known for sure", the first digit that we know for sure is the tens digit, which is known to be zero; that would give 0.?e1, which gives vastly less information than 1.000000?. Perhaps the docstring you quote should be adjusted? Elsewhere (in the module docstring) we find this variant: In question style, we print the "known correct" part of the number, followed by a question mark. The question mark indicates that the preceding digit is possibly wrong by +/- 1. Maybe that second sentence should be copied into the docstring for .str()? Carl --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
