On Monday, June 12, 2017 at 4:01:19 PM UTC-7, William wrote: > > > What is your definition of "hashable"? I always thought of hashable > as basically > synonymous with "immutable", except for issues of efficiency. Aren't > floating points > numbers at least immutable, even if there are various other issues with > them? > > OK, probably floats are OK if you interpret them as a finite subset of real numbers that are representable in the chosen representation. Once you start mixing precisions, you might violate hash/equality assumptions, though:
sage: R1=RealField(100) sage: R2=RealField(20) sage: a=R1(pi) sage: b=R2(a) sage: a==b True sage: hash(a)==hash(b) False (most of the time this might be OK, though: hash is implemented as hash(float(...)), so apart from rounding accidents, hashes of floats at precisions > 53 should be OK) -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
