Hey Jeffrey,
it's been a while, thx for the answer. I see that this would be working.
However, what about min, max, sin, etc.? I do not want to re-implement all
elementary functions for the Probability type. There must be some way to
inherit the behaviour of the abstract supertype "Real". I guess I am
missing something fundamental about the type system here.
I felt tat something like
type Probability{T<:Real} <:Real
p::T
end
import Base.convert
convert{T<:Real}(::Type{T}, x::Probability) = convert(T, x.p)
convert{T1<:Real, T2<:Real}(::Type{Probability{T1}}, x::T2) =
Probability(convert(T1, x))
should do the job as now any Probability can be converted to any concrete
subtype of Real and "+" shoud be implemented there ;)
Very strange, how does Julia handle inheritance at all???
Best,
Kevin
On Monday, 29 February 2016 23:45:35 UTC+1, Jeffrey Sarnoff wrote:
>
> Kevin,
>
> If all that you ask of this type is that it does arithmetic, clamps any
> negative values to zero, and clamps any values greater than one to one,
> that is easy enough. Just note that arithmetic with probabilities usually
> is more subtle than that.
>
> import Base: +,-,*,/
>
> immutable Probability <: Real
> val::Float64
>
> Probability(x::Float64) = min(1.0, max(0.0, x))
> end
>
> (+){T<:Probability}(a::T, b::T) = Probability( a.val + b.val )
> (-){T<:Probability}(a::T, b::T) = Probability( a.val - b.val )
> (*){T<:Probability}(a::T, b::T) = Probability( a.val * b.val )
> (/){T<:Probability}(a::T, b::T) = Probability( a.val / b.val )
>
> You need conversion and promotion if you want to mix Float64 values and
> Probability values: 2.0 * Probability(0.25) == Probability(0.5).
>
> On Sunday, February 28, 2016 at 10:33:07 AM UTC-5, Kevin Kunzmann wrote:
>>
>> Hey,
>>
>> I have a (probably) very simple question. I would like to define
>> 'Probability' as a new subtype of 'Real', only with the additional
>> restriction that the value must be between 0 and 1. How would I achieve
>> that 'Julia-style'? This should be possible without having to rewrite all
>> these promotion rules and stuff, is it not?
>>
>> Best Kevin
>>
>
