Example of a Rust generator and a corresponding Iterator.

generator_eg.rs

#![feature(generators, generator_trait)]

use std::{
    iter,
    ops::{Generator, GeneratorState},
    pin::Pin,
};

pub struct Grid<const R: usize, const C: usize> {
    grid: [[bool; C]; R],
}

impl<const R: usize, const C: usize> Grid<R, C> {
    pub fn col<'a>(&'a self, idx: usize) -> impl Iterator<Item = bool> + 'a {
        let mut i = 0;
        let mut gen = move || {
            while i < R {
                yield self.grid[i][idx];
                i += 1;
            }
            return;
        };
        iter::from_fn(move || match Pin::new(&mut gen).resume(()) {
            GeneratorState::Yielded(val) => Some(val),
            GeneratorState::Complete(_) => None,
        })
    }
}