specializations.rs

extern crate itertools;

use itertools::{Itertools, EitherOrBoth};

use std::fmt::Debug;
use std::ops::BitXor;

struct Unspecialized<I>(I);
impl<I> Iterator for Unspecialized<I>
where
    I: Iterator,
{
    type Item = I::Item;

    #[inline(always)]
    fn next(&mut self) -> Option<I::Item> {
        self.0.next()
    }

    #[inline(always)]
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.0.size_hint()
    }
}

fn check_specialized<'a, V, IterItem, Iter, F>(iterator: &Iter, mapper: F)
where
    V: Eq + Debug,
    IterItem: 'a,
    Iter: Iterator<Item = IterItem> + Clone + 'a,
    F: Fn(Box<Iterator<Item = IterItem> + 'a>) -> V,
{
    assert_eq!(
        mapper(Box::new(Unspecialized(iterator.clone()))),
        mapper(Box::new(iterator.clone()))
    )
}

fn check_specialized_count_last_nth_sizeh<'a, IterItem, Iter>(it: &Iter, expected_size: usize)
where
    IterItem: 'a + Eq + Debug,
    Iter: Iterator<Item = IterItem> + Clone + 'a,
{
    let size = it.clone().count();
    assert_eq!(size, expected_size);
    check_specialized(it, |i| i.count());
    check_specialized(it, |i| i.last());
    for n in 0..size + 2 {
        check_specialized(it, |mut i| i.nth(n));
    }
    let mut it_sh = it.clone();
    for n in 0..size + 2 {
        let len = it_sh.clone().count();
        let (min, max) = it_sh.size_hint();
		assert_eq!((size-n.min(size)), len);
        assert!(min <= len);
        if let Some(max) = max {
            assert!(len <= max);
        }
		it_sh.next();
    }
}

fn check_specialized_fold_xor<'a, IterItem, Iter>(it: &Iter)
where
    IterItem: 'a
        + BitXor
        + Eq
        + Debug
        + BitXor<<IterItem as BitXor>::Output, Output = <IterItem as BitXor>::Output>
        + Clone,
    <IterItem as BitXor>::Output:
        BitXor<Output = <IterItem as BitXor>::Output> + Eq + Debug + Clone,
    Iter: Iterator<Item = IterItem> + Clone + 'a,
{
    check_specialized(it, |mut i| {
        let first = i.next().map(|f| f.clone() ^ (f.clone() ^ f));
        i.fold(first, |acc, v: IterItem| acc.map(move |a| v ^ a))
    });
}

#[test]
fn put_back() {
    let test_vec = vec![7, 4, 1];
    let pb = itertools::put_back(test_vec.iter());
    check_specialized_count_last_nth_sizeh(&pb, 3);
    check_specialized_fold_xor(&pb);

    let mut pb = itertools::put_back(test_vec.into_iter());
    pb.put_back(1);
    check_specialized_count_last_nth_sizeh(&pb, 4);
    check_specialized_fold_xor(&pb);
}

#[test]
fn merge_join_by() {
    let i1 = vec![1, 3, 5].into_iter();
    let i2 = vec![0, 3, 4, 5].into_iter();
    let mjb = i1.merge_join_by(i2, std::cmp::Ord::cmp);
    check_specialized_count_last_nth_sizeh(&mjb, 5);
	// Rust 1.24 compatibility:
	fn eob_left_z(eob: EitherOrBoth<usize, usize>) -> usize { eob.left().unwrap_or(0) }
	fn eob_right_z(eob: EitherOrBoth<usize, usize>) -> usize { eob.left().unwrap_or(0) }
	fn eob_both_z(eob: EitherOrBoth<usize, usize>) -> usize { let (a,b) = eob.both().unwrap_or((0,0)); assert_eq!(a,b); a }
    check_specialized_fold_xor(&mjb.clone().map(eob_left_z));
    check_specialized_fold_xor(&mjb.clone().map(eob_right_z));
    check_specialized_fold_xor(&mjb.clone().map(eob_both_z));
}