Bill Page wrote: > > On 10 September 2016 at 08:38, Waldek Hebisch <[email protected]> > wrote: > >> > >> What's the right thing to do? > >> > >> (1) -> 0.0 ^ (0::NNI) > >> > >> (1) 1.0 > >> Type: > >> Float <snip> > > For approximate exponents it make sense to leave it undefiend > > (and signal errors when users try to use it). > > > > Are 0$DFLOAT and 1$DFLOAT really only approximate in FriCAS? In > general I thought the most consistent approach to floats was to treat > all (representable) floating point numbers as exact but to admit that > floating point operations are often necessarily approximate.
If a function gets 0 as an argument, then there is good chance to this 0 is mathematically correct. But when mathematically you should get 0, rounding error may lead to small nonzero number. Given that x^y is discontinous at (0,0), depending on definition of x^y at (0, 0) is error prone. So it makes sense to "undefine" it and signal error. > Apparently before SBCL 1.0.41.47, SBCL used to return > > (expt 0.0 0.0) -> 1.0 > > https://bugs.launchpad.net/sbcl/+bug/571581 > > But is there any good reason that FriCAS should follow this "standard"? I do not understand your position here. First you argue that we should treat it as exact case, so return 1. Then you apparently have opposite position... -- Waldek Hebisch -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" 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/fricas-devel. For more options, visit https://groups.google.com/d/optout.
