dedenne's Introduction

Dedenne

Cute little generators!

Dedenne implements generators, a la the unstable language feature, over async/await in completely stable Rust.

Simple Usage

use dedenne::*;

let mut generator = Generator::new(|y, init| async move {
  for x in 0..init {
    y.ield(x).await;
  }
  for x in (0..init).rev() {
    y.ield(x).await;
  }

  "All done!"
});

assert_eq!(
  generator.start(3), GeneratorResponse::Yielding(0)
);
assert_eq!(
  generator.resume(), GeneratorResponse::Yielding(1)
);
assert_eq!(
  generator.resume(), GeneratorResponse::Yielding(2)
);
assert_eq!(
  generator.resume(), GeneratorResponse::Yielding(2)
);
assert_eq!(
  generator.resume(), GeneratorResponse::Yielding(1)
);
assert_eq!(
  generator.resume(), GeneratorResponse::Yielding(0)
);
assert_eq!(
  generator.resume(), GeneratorResponse::Done("All done!")
);

For a larger example, check out this simple TUI interface.

`panic!` vs `unreachable!`

If something in Dedenne panic!s, then it's a user error. Make sure to await your y.ields, and don't call resume after a generator's exhausted.

If something in Dedenne panics with an unreachable! message, then it's a problem with Dedenne. Please file a bug report if it does.

Prior Art

I am not the first person to have this idea. However, I think Dedenne is the only crate that supports mapping over iterators.

generator. Doesn't support a starting argument, which means you can't use it as a mapping iterator. Is always stackful.
genawaiter. Has some convenience macros that make it nicer to make generators. Also lets you really tune how the generators are stored (stackful or allocating).
Unstable lang feature. Doesn't support passing values in to a generator, afaict. Also requires nightly rust and has been bikeshedding for 6 years as of time of writing.

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