Simon's example:
type EulerAngles{SEQ,T}
a::Vector{T}
end
call{T <: Number, SEQ}(::Type{EulerAngles{SEQ}}, a::Vector{T}) =
EulerAngles{SEQ, T}(a)
julia> EulerAngles{123}([10.0,20.0,30.0])
EulerAngles{123,Float64}([10.0,20.0,30.0])
On Wednesday, August 26, 2015 at 8:56:55 AM UTC-4, Simon Danisch wrote:
>
> First of all I would recommend FixedSizeArrays or NTuples for this, as
> they can be faster in some cases and you can restrict them to 3 dimensions.
> Then I'd follow Tim Holy's advice.
> Concerning your problem, you can do this on 0.4:
>
> call{T <: Number, SEQ}(::Type{EulerAngles{SEQ}, a::Vector{T}} =
> EulerAngles{SEQ, T}(a)
>
> Best,
> Simon
>
>
> Am Mittwoch, 26. August 2015 05:29:08 UTC+2 schrieb [email protected]:
>>
>> 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
>>
>
