Only partially relevant, but my general reaction to Euler angles is: don't do it, because of gimbal lock. https://github.com/forio/Quaternions.jl and https://github.com/timholy/AffineTransforms.jl have algorithms that are not vulnerable to this problem.
Take this advice with a grain of salt, of course; they're still out there, and may be useful under some circumstances. --Tim On Tuesday, August 25, 2015 08:29:08 PM [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
