Rust code shared from the playground

playground.rs

#![feature(conservative_impl_trait)]

use std::iter::{self};

fn main() {
    println!("{:?}", difference([0, 1, 2].iter(), [2, 3, 4].iter()).collect::<Vec<_>>());
    println!("{:?}", union([0, 1, 2].iter(), [2, 3, 4].iter()).collect::<Vec<_>>());
    println!("{:?}", intersection([0, 1, 2].iter(), [2, 3, 4].iter()).collect::<Vec<_>>());
}

fn difference<A, B, I>(a: A, b: B) -> impl Clone + Iterator<Item=I> where A: Clone + Iterator<Item=I>, B: Clone + Iterator<Item=I>, I: Clone + Eq {
    fn filter<A, I>(v: (I, A)) -> Option<I> where A: Clone + Iterator<Item=I>, I: Clone + Eq {
        fn eq<I>(i: (I, &I)) -> bool where I: Eq {
            i.0 == *i.1
        }
        
        if !v.1.zip(iter::repeat(&v.0)).any(eq) {
            Some(v.0)
        } else {
            None
        }
    }
    
    a.zip(iter::repeat(b)).filter_map(filter)
}

fn union<A, B, I>(a: A, b: B) -> impl Clone + Iterator<Item=I> where A: Clone + Iterator<Item=I>, B: Clone + Iterator<Item=I>, I: Clone + Eq {
    a.clone().chain(difference(b, a))
}

fn intersection<A, B, I>(a: A, b: B) -> impl Clone + Iterator<Item=I> where A: Clone + Iterator<Item=I>, B: Clone + Iterator<Item=I>, I: Clone + Eq {
    fn filter<A, I>(v: (I, A)) -> Option<I> where A: Clone + Iterator<Item=I>, I: Clone + Eq {
        fn eq<I>(i: (I, &I)) -> bool where I: Eq {
            i.0 == *i.1
        }
        
        if v.1.zip(iter::repeat(&v.0)).any(eq) {
            Some(v.0)
        } else {
            None
        }
    }
        
    a.zip(iter::repeat(b)).filter_map(filter)
}