[Question] Having hard time trying to create a chunk out to a function

[fatboyzz]

use anyhow::Result;
use itertools::Itertools;

fn main() -> Result<()> {
    let ns = vec![2, 2, 3, 3, 4, 4, 5, 5];

    let chunk = ns.iter().chunk_by(|n| *n % 2 == 0);
    // let chunk = chunked(ns.iter());

    let group = chunk.into_iter().take(2);
    for (even, ns) in group {
        println!("{} {:?}", even, ns.collect::<Vec<_>>());
    }
    Ok(())
}

// Don't know how to write the return type.
// Note that impl IntoIterator is not an option.
// the trait `IntoIterator` is implemented 
// - for `&itertools::ChunkBy<K, I, F>`
// - not `itertools::ChunkBy<K, I, F>`
//
// fn chunked(ns: impl Iterator<Item = i32>) -> impl IntoIterator {
//   ns.chunk_by(|n| *n % 2 == 0)
// }

• playground

[phimuemue]

Very ugly, but this may serve as a start:

use anyhow::Result;
use itertools::Itertools;

fn main() -> Result<()> {
    let ns = vec![2, 2, 3, 3, 4, 4, 5, 5];

    let chunk = ns.iter().chunk_by(|n| *n % 2 == 0);
    let chunk = chunked(ns.iter().copied());

    let group = chunk.into_iter().take(2);
    for (even, ns) in group {
        println!("{} {:?}", even, ns.collect::<Vec<_>>());
    }
    Ok(())
}

fn chunked(ns: impl Iterator<Item = i32>) ->
    itertools::ChunkBy<
        bool,
        impl Iterator<Item = i32>,
        impl FnMut(&i32)->bool
    >
{
   ns.chunk_by(|n| *n % 2 == 0)
}

[fatboyzz]

we can define chunked<I> where I is that Iterator. to not repeat the Iterator type.
also can't add F for the FnMut. Have to use the impl in return type.