Are you looking to do this?
julia> type EulerRotation{I,J,K}
angles::Vector{Float64}
end
julia> function getEulerAngleSeq(x::EulerRotation)
p = typeof(x).parameters
Float64[x.angles[i] for i in p]
end
getEulerAngleSeq (generic function with 1 method)
julia> testRotSeq321 = EulerRotation{3,2,1}([1.0,2.0,3.0])
EulerRotation{3,2,1}([1.0,2.0,3.0])
julia> getEulerAngleSeq(testRotSeq321)
3-element Array{Float64,1}:
3.0
2.0
1.0
julia> testRotSeq132 = EulerRotation{1,3,2}([1.0,2.0,3.0])
EulerRotation{1,3,2}([1.0,2.0,3.0])
julia> getEulerAngleSeq(testRotSeq132)
3-element Array{Float64,1}:
1.0
3.0
2.0
On Tuesday, August 25, 2015 at 11:29:08 PM UTC-4, [email protected] wrote:
>
> Hi, everyone.
>
> I've been tinkering with creating a package for dealing with Euler angles,
> using a very recent build of v0.4. Rather than just rehash Matlab's
> functions, I wanted to take advantage of the type system, to learn more
> about parametric types and constructors.
>
> I definitely want the Euler rotation sequence and the angles to be bound
> together. One straightforward way to do this would of course be:
>
> type EulerAngles{T <: Number}
> seq::Int
> angles::Vector{T}
> end
>
> Which would work fine, but I'd end up with a huge if block for every valid
> sequence. So I thought I'd try moving the sequence into the type
> definition. I think I would declare the type like this:
>
> type EulerAngles{T <: Number, s}
> angles::Vector{T}
> end
>
> But then I can't figure out the best way to provide constructors for this
> type. What I want is something like this:
>
> EulerAngles{321}([1.0, 2.0, 3.0])
>
> But I can't figure out how to get this to work. Is this kind of
> constructor even possible with the type I showed above?
>
> I was able to get something very similar to work, by making functions that
> look like constructors with the sequence in their names, like this:
>
> EulerAngles321([1.0, 2.0, 3.0])
>
> Which works, but gives the impression that EulerAngles321 is actually a
> type. But it seems that typealiases can't have constructors, and I get an
> error trying to define a typealias and a function with the same name. Even
> with this limitation, though, this seems like an OK solution.
>
> If I really wanted to have types with those names, I could have an
> abstract EulerAngles type, and then have concrete types like
> EulerAngles321. But that seems like overkill (in terms of the number of
> types I'd create). Though it would work.
>
> Does anyone have any guidance on how to best approach this?
>
> Thanks for the help!
>
> Daniel
>
