FFT Proc Block => V2 proc block about rune

[Michael-F-Bryan]

Here are some useful links:

• the initial FFT implementation
• The normalize implementation shows how a proc block can be generic over anything which you can turn into a mutable/immutable slice
• The modulo implementation s- hows how you can make the proc block work for both individual items and fixed-size arrays of items.
• FFT Crates:
  • Docs for the sonogram crate used in the initial implementation
  • The fixed-fft crate an alternative to sonogram which is no_std
  • The microfft crate

[Michael-F-Bryan]

@kthakore building microspeech currently fails because sonogram doesn't compile without the standard library:

cargo rune build examples/microspeech/Runefile
    Finished release [optimized] target(s) in 0.07s
     Running `target/release/rune build examples/microspeech/Runefile`
[2021-03-18T14:34:59.601Z DEBUG rune::build] Parsing "examples/microspeech/Runefile"
[2021-03-18T14:34:59.601Z DEBUG rune::build] Compiling microspeech in "/home/michael/.cache/runes/microspeech"
[2021-03-18T14:34:59.601Z DEBUG rune_codegen] Executing "cargo" "build" "--target=wasm32-unknown-unknown" "--quiet" "--release"
error[E0599]: no method named `round` found for type `f32` in the current scope
  --> /home/michael/.cargo/git/checkouts/sonogram-bce1c9fece1bdf09/caf3d4b/src/colour_gradient.rs:96:73
   |
96 |     ((f32::from(finish) - f32::from(start)) * ratio + f32::from(start)).round() as u8
   |                                                                         ^^^^^ method not found in `f32`
   |
   = help: items from traits can only be used if the trait is in scope
   = note: the following trait is implemented but not in scope; perhaps add a `use` for it:
           `use num::traits::float::FloatCore;`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.
error: could not compile `sonogram`

To learn more, run the command again with --verbose.
error: build failed
Error: Rune compilation failed

Caused by:
    Compilation failed

I think we should be using libm::roundf() instead.

[Michael-F-Bryan]

This was fixed in #152.