Re: [julia-users] Re: Trait for exactness of numbers
I see thank you very much for your answer! :D El martes, 25 de octubre de 2016, 13:20:50 (UTC-5), Tim Holy escribió: > > > Why not use dispatch instead? > > Because subtyping isn't powerful enough for all needs. For example: > > > julia> using Unitful > > julia> const mm = u"mm" > mm > > julia> isa(3.2mm, AbstractFloat) > false > > > You'd probably like to use the fancy logic of `FloatRange` if you're > constructing a range `3.2mm:0.1mm:4.8mm`, so the solution is to dispatch on > a trait that indicates that arithmetic isn't exact (which is what really is > going on inside that code anyway---who cares what kind of number type it > is). > > Best, > --Tim > > On Tue, Oct 25, 2016 at 12:55 PM, Ismael Venegas Castelló < > ismael...@gmail.com > wrote: > >> Why not use dispatch instead? >> >> isexact(::Integer) = true >> isexact(::Rational) = true >> isexact(x::Complex) = isexact(x.re) >> isexact(::Any) = false > > >
Re: [julia-users] Re: Trait for exactness of numbers
> Why not use dispatch instead? Because subtyping isn't powerful enough for all needs. For example: julia> using Unitful julia> const mm = u"mm" mm julia> isa(3.2mm, AbstractFloat) false You'd probably like to use the fancy logic of `FloatRange` if you're constructing a range `3.2mm:0.1mm:4.8mm`, so the solution is to dispatch on a trait that indicates that arithmetic isn't exact (which is what really is going on inside that code anyway---who cares what kind of number type it is). Best, --Tim On Tue, Oct 25, 2016 at 12:55 PM, Ismael Venegas Castelló < ismael.vc1...@gmail.com> wrote: > Why not use dispatch instead? > > isexact(::Integer) = true > isexact(::Rational) = true > isexact(x::Complex) = isexact(x.re) > isexact(::Any) = false
[julia-users] Re: Trait for exactness of numbers
Why not use dispatch instead? isexact(::Integer) = true isexact(::Rational) = true isexact(x::Complex) = isexact(x.re) isexact(::Any) = false
Re: [julia-users] Re: Trait for exactness of numbers
+1. We need number traits for a variety of circumstances; I was also
contemplating them as a step in generalizing the FloatRange/StepRange
distinction, for example to Unitful numbers (numbers with physical units).
You need type-stability for the created range object, so I think a trait is
the only way to go here.
--Tim
On Mon, Oct 24, 2016 at 3:30 PM, Jeffrey Sarnoff
wrote:
> for values, something like this may do:
>
> function isexact(x)
> if isa(x, Integer) || isa(x, Rational)
> true
> elseif isa(x, Complex)
> isExact(x.re)
> else
> false
> end
> end
>
>
>
>
> On Monday, October 24, 2016 at 2:09:09 PM UTC-4, jw3126 wrote:
>>
>> A couple of times I was in a situation, where I had two algorithms
>> solving the same problem, one which was faster and one which was more
>> numerically stable. Now for some types of numbers (FloatingPoint,
>> Complex{Float64}...) numerical stability is important while for others it
>> does not matter (e.g. Integer, Complex{Int64}...) etc.
>> In such situations it would be handy to have a mechanism (a trait) which
>> decides whether a type is exact or prone to rounding.
>> Maybe there is already such a thing somewhere?
>>
>
[julia-users] Re: Trait for exactness of numbers
for values, something like this may do:
function isexact(x)
if isa(x, Integer) || isa(x, Rational)
true
elseif isa(x, Complex)
isExact(x.re)
else
false
end
end
On Monday, October 24, 2016 at 2:09:09 PM UTC-4, jw3126 wrote:
>
> A couple of times I was in a situation, where I had two algorithms solving
> the same problem, one which was faster and one which was more numerically
> stable. Now for some types of numbers (FloatingPoint, Complex{Float64}...)
> numerical stability is important while for others it does not matter (e.g.
> Integer, Complex{Int64}...) etc.
> In such situations it would be handy to have a mechanism (a trait) which
> decides whether a type is exact or prone to rounding.
> Maybe there is already such a thing somewhere?
>
