Be generic over both Input and Output sample types

[mitchmindtree]

It looks like we're about to hit the classic use-case for associated types!

I just realised there are a couple changes that need to be made to the Node's audio_received method (not included in the test example).

• Rather than taking B where B DspBuffer<O>, O: OutputSample, audio_received should take Vec<I> where I: InputSample
• This means our trait should probably be Node<B, I, O> where B: DspBuffer<O>, I: InputSample, O: OutputSample

The amount of type parameters will likely get very frustrating very quickly, but we'll be able to clean up nicely once associated types land.

[mitchmindtree]

I'm going to have a go at using the feature gated associated types, just to see how far I get...

[mitchmindtree]

Didn't get very far at all! I'll change it over to Node<B=Vec<f32>, I=f32, O=f32> until assoc types stabilise a bit further

[bvssvni]

One day... the associated types will prevail! :P

[mitchmindtree]

This was implemented (I accidently pushed it straight to the repo)

[mitchmindtree]

@bvssvni this just landed! https://github.com/rust-lang/rust/blob/ce4318ad86f2ccd0710247020269ba0ba22c6d59/src/test/run-pass/assoc-eq.rs

Might have another go at this tonight

[bvssvni]

This is exciting!

[mitchmindtree]

This has been implemented and the abstraction has it's own crate.