WIP: Address Crystal 0.36.1 complaints and latest alea update

[lbarasti]

Hi folks, this is to start the conversation on what needs to be done to ensure num.cr works with the latest version of alea (which now requires Crystal v0.36.0 or greater).

See #63

[christopherzimmerman]

Is the issue with this that child methods sometimes say args is an instance of Num::Grad::Variable, which isn't explicitly defined by the abstract base, or that args must now have a defined type?

cache methods can take anything that a gate needs to store information. For example, the convolutional gate's cache method also takes tuples of integers for padding and stride.

[lbarasti]

Hey Chris, the issue is the compiler now complains that the implementations are too strict

In src/grad/gates_blas.cr:25:1

 25 | class Num::Grad::MatMulGate(T) < Num::Grad::Gate(T)
      ^
Error: abstract `def Num::Grad::Gate(T)#cache(result : Num::Grad::Variable(T), *args)` must be implemented by Num::Grad::MatMulGate(T)

So either we restrict the abstract def or we remove the type restriction on each def cache definition

[christopherzimmerman]

Thank you for the PR. I haven't had time to work much on this library recently, but I will double check tomorrow to make sure everything works with the most recent version.

[christopherzimmerman]

@lbarasti closing this in favor of the now merged #65. I still need to do some work with library dependencies, to make transitions smoother.