Thanks -- I wasn't aware that a^b is irrational in general in this case. Now I wonder if a Float is a better approximation to an irrational number than a Rational.
Of course, one could say that sqrt(a) is complex in general for real a, but Julia returns a real. As Stefan says, some of these cases have no good solutions, only less worse ones. -- mb On Sun, Jun 8, 2014 at 7:09 PM, 'Stéphane Laurent' via julia-users < julia-users@googlegroups.com> wrote: > If b is rational then a^b is irrational in general, even for a integer, so > this output is quite expected, as well as > > julia> (10//1)^(2//1) > > 100.0 > > > > > Le lundi 9 juin 2014 00:54:37 UTC+2, Miguel Bazdresch a écrit : >> >> I just tried this (on 0.2.1): >> >> julia> (10//1)^(-2//1) >> 0.01 >> >> Is this expected? >> >> -- mb >> >> >> >> On Sun, Jun 8, 2014 at 6:36 PM, 'Stéphane Laurent' via julia-users < >> julia...@googlegroups.com> wrote: >> >>> julia> (10//1)^(-2) >>> >>> 1//100 >>> >>> >>> Would it be problematic to return a rational >>> for (a::Integer)^(b::Integer) ? >>> >>> >>> >>> Le dimanche 8 juin 2014 21:53:45 UTC+2, Stefan Karpinski a écrit : >>>> >>>> There are three obvious options for (a::Integer)^(b::Integer): >>>> >>>> 1. Always return an integer ⟹ fails for negative b. >>>> 2. Always return a float ⟹ a^2 is not the same as a*a. >>>> 3. Return float for negative b, integer otherwise ⟹ not type-stable. >>>> >>>> As you can see, all of these choices are problematic. The first one, >>>> which is what we currently do, seems to be the least problematic. One >>>> somewhat crazier option that has been proposed is making ^- as in a^-b >>>> parse as a different operator and have a^b return an integer for integer >>>> arguments but a^-b return a float for integer arguments. This would have >>>> the unfortunate effect of making a^-b different from a^(-b). >>>> >>>> >>>> On Sat, Jun 7, 2014 at 12:41 PM, Daniel Jones <daniel...@gmail.com> >>>> wrote: >>>> >>>>> I'd definitely be in favor of '^' converting to float, like '/', >>>>> having fallen for than recently >>>>> <https://github.com/JuliaLang/Color.jl/commit/c3d05dd2b94f0d38b64ef86022accdfec886a673> >>>>> . >>>>> >>>>> On Sat, Jun 7, 2014, at 12:53 AM, Ivar Nesje wrote: >>>>> > >>>>> > There has also been discussion on whether ^(a::Integer,b::Integer) >>>>> should >>>>> > return a Float64 by default, and defer to pow() like /(a::Integer, >>>>> > b::Integer) defers to div(). The problem is that many people like the >>>>> > 10^45 vs 1e45 notation for large integers vs float constants, and we >>>>> can >>>>> > make it a clean error instead of a silent bug. >>>>> >>>>> >>>> >>>> >>
