Softtype as an instance or a type, T vs T()

[Affie]

Softtype is now a singleton type and to avoid confusion we have to decide whether it will be used as an instance or a type.
for example:
getManifolds(::Type{Pose2}) vs getManifolds(::Pose2)
For compatibility, I used an instance where @dehann used type getManifolds(vartype::Type{LinearConditional}) = (:Euclid,)

It doesn't seem to make a performance difference.

[dehann]

I'd suggest only the ::Type{T}, i.e. addVariable!(..., Pose2). It's much cleaner and doesn't pollute with parenthesis everywhere.

[dehann]

its also easy to just do T() internally if needed, but its more difficult to go back obj --> ::Type{T}

[dehann]

Hi Johan, how do you feel about this?

const InstanceType{T} = Union{Type{<:T},T}

[Affie]

Hi Johan, how do you feel about this?

const InstanceType{T} = Union{Type{<:T},T}

I don't know how that will help. You need something like this discouraged pattern in the style guide:

foo(::Type{MyType}) = ..
foo(::MyType) = foo(MyType)

EDIT: Ok, I see how you use it in RoME. I was thinking of addVariable!

From a user side,

• I think the type is easier as: addVariable!(..., Pose2)
• I find functions of this form easier to work with: getManifolds(::Pose2) but I created a macro so one can generate and change it easily.

For now, my vote would be to just follow the style guide :

The preferred style is to use instances by default, and only add methods involving Type{MyType} later if they become necessary to solve some problem.

[dehann]

For now, my vote would be to just follow the style guide
I think the type is easier as: addVariable!(..., Pose2)

I'm also in the camp of using the type, but I don't know how this influences type stability. I'm assuming ::DataType is not stable hence the suggestion to work with instances... I think we can come back to this. This feels like a minor performance, but much larger user experience thing. Let's wait on a decision for now.

[Affie]

I came across this thread https://discourse.julialang.org/t/singleton-types-vs-instances-as-type-parameters/2802/11

Maybe it can be a tie breaker.