use std::collections::{vec_deque, VecDeque};
use std::fmt;
use std;

#[derive(Debug)]
pub struct LimitedFifoQueue<T> {
    size: usize,
    store: VecDeque<T>,
}

impl<T> LimitedFifoQueue<T> where T: fmt::Display {
    pub fn new(size: usize) -> LimitedFifoQueue<T> {
        LimitedFifoQueue {
            size: size,
            store: VecDeque::with_capacity(size),
        }
    }
    pub fn push(&mut self, elem: T) {
        self.store.push_front(elem);
        if self.store.len() > self.size {
            self.store.pop_back();
        }
    }
    pub fn clear(&mut self) {
        self.store.clear();
    }
}

impl<T> IntoIterator for LimitedFifoQueue<T> where T: fmt::Display {
    type Item = T;
    type IntoIter = vec_deque::IntoIter<T>;
    fn into_iter(self) -> Self::IntoIter {
        self.store.into_iter()
    }
}

fn print_all<I>(lines: &I) where I: IntoIterator {
    for string in lines.into_iter() {
        println!("{}", string);
    }
}

fn print_all<I>(lines: I)
    where I: IntoIterator,
          I::Item: fmt::Display,
{
    for string in lines.into_iter() {
        println!("{}", string);
    }
}

fn print_all<I>(lines: I)
    where I: IntoIterator,
          I::Item: fmt::Display,
{
    for string in lines {
        println!("{}", string);
    }
}

fn print_all<I>(lines: &I) where I: IntoIterator {
    for string in lines.into_iter() {
        println!("{}", string);
    }
}

fn print_all<I>(lines: &I)
    where I: IntoIterator,
          I::Item: fmt::Display,
{ ... }