Impossible to compile DQNAgent outside of crate

[stiff]

When crate rl is added via cargo, implementing ToTensor compiler gives error:

error[E0210]: type parameter `B` must be used as the type parameter for some local type (e.g., `MyStruct<B>`)
  --> src/main.rs:29:6
   |
29 | impl<B: Backend<IntElem = i32>> ToTensor<B, 2, Int> for Vec<HAction> {
   |      ^ type parameter `B` must be used as the type parameter for some local type
   |
   = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
   = note: only traits defined in the current crate can be implemented for a type parameter

Or am I missing something?

Version: 0.4.0
Agent is basically from dqn cart pole example, just stripped away gym and viz (to localize error).

[stiff]

Installed latest version from git, and see it is already changed. But it's still impossible, because Vec<E::Action> is required to implement ToTensor in https://github.com/benbaarber/rl/blob/main/src/algo/dqn.rs#L158
Changing my custom env Action to [i32; 2] (because ToTensor is implemented for [i32, _]) is impossible because on the next line it's required to implement From https://github.com/benbaarber/rl/blob/main/src/algo/dqn.rs#L159

Specifically, this implementation https://github.com/benbaarber/rl/blob/main/src/gym/cart_pole.rs#L34 is impossible for environments defined outside of this crate

[stiff]

This is a possible fix: stiff@eeda151 though I don't fully like it, but works now. Can open PR

[benbaarber]

Thanks for opening the issue! Am working on an update to the crate to use the new version of burn (v16) among other things. The ToTensor trait was an unpolished initial stab at generalizing the algorithms, and I'm working on a better approach that will solve this issue. Been pretty busy with other things so progress is slow, but stay tuned for the next version. Appreciate you trying out the library dude!

[stiff]

I also noticed that it's not really possible to save trained model, because DQNAgent takes a model but not exposing it.

Wanted to quickly try an idea, and found this nice create, thanks for good job, spotted issues are minor and can be easily fixed.