fn next(&mut self) -> Option<A::Item> {
        match self.state {
            State::Both => match self.a.next() {
                elt @ Some(..) => elt,
                None => {
                    self.state = State::Back;
                    self.b.next()
                }
            },
            State::Front => self.a.next(),
            State::Back => self.b.next(),
        }
    }
// This is the function we care about
This is the function we care about
This is the function we care about
fn next(&mut self) -> Option<A::Item> {
        match self.state {
            State::Both => match self.a.next() {
                elt @ Some(..) => elt,
                None => {
                    self.state = State::Back;
                    self.b.next()
                }
            },
            State::Front => self.a.next(),
            State::Back => self.b.next(),
        }
    }
fn next ( & mut self ) -> Option < A :: Item > { match self . state { State :: Both => match self . a . next ( ) { elt @ Some ( .. ) => elt , None => { self . state = State :: Back ; self . b . next ( ) } } , State :: Front => self . a . next ( ) , State :: Back => self . b . next ( ) , } }
This is the function we care about
This is the function we care about
&mut self
&mut self