On Wed, Mar 11, 2009 at 9:35 PM, Robert Bradshaw <rober...@math.washington.edu> wrote: >> Here's some examples to hopefully clarify: > > >> RealField(20) -> RealField(50) >> RealField(20) -> RealIntervalField(20) > > I would call these dangerous, as the latter implicitly has more > "information" than the former.
No they don't: sage: pi20.exact_rational() 411775/131072 sage: RealField(50)(pi20).exact_rational() 411775/131072 See, exactly the same information :) Remember that in my proposal, these "safe" coercions/conversions (I said I needed a better name!) are only used for comparisons and "in". The effect is that since RealField(20)->RealField(50) is a safe conversion (not a coercion!), and RealField(50)->RealField(20) is an unsafe coercion, RealField(20)(pi)==RealField(50)(pi) would return False. (I want this behavior a lot more often than I want the current behavior, where this equality test gives True.) 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 -~----------~----~----~----~------~----~------~--~---
