timsort 0.1.3

Rust implementation of the modified MergeSort used in Python and Java
Documentation 
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//! The merge algorithm. This one can merge unequal slices, allocating an n/2
//! sized temporary slice of the same type. Naturally, it can only merge slices
//! that are themselves already sorted.

use crate::{comparator, never, ord_t_comparator};

/// Test mergeing two empty slices.
#[test]
fn empty() {
    let mut list: Vec<u32> = vec![];
    merge(&mut list, 0);
    assert!(list.is_empty());
}

/// Test merging two equal-sized single-element vectors that are already sorted.
#[test]
fn single_sorted() {
    let mut list = vec![42, 90];
    merge(&mut list, 1);
    assert!(list[0] == 42);
    assert!(list[1] == 90);
}

/// Test merging two equal-sized single-element vectors that are already sorted.
#[test]
fn single_unsorted() {
    let mut list = vec![90, 42];
    merge(&mut list, 1);
    assert!(list[0] == 42);
    assert!(list[1] == 90);
}

/// Test merging two unequal-sized vectors.
#[test]
fn hi_unsorted() {
    let mut list = vec![90, 17, 42];
    merge(&mut list, 1);
    assert!(list[0] == 17);
    assert!(list[1] == 42);
    assert!(list[2] == 90);
}

/// Test merging two unequal-sized vectors.
#[test]
fn lo_unsorted() {
    let mut list = vec![17, 90, 42];
    merge(&mut list, 2);
    assert!(list[0] == 17);
    assert!(list[1] == 42);
    assert!(list[2] == 90);
}

/// Test merging two unequal-sized vectors.
#[test]
fn hi_unsorted_multiple() {
    let mut list = vec![21, 32, 91, 17, 20, 40, 80];
    merge(&mut list, 3);
    assert!(list[0] == 17);
    assert!(list[1] == 20);
    assert!(list[2] == 21);
    assert!(list[3] == 32);
    assert!(list[4] == 40);
    assert!(list[5] == 80);
    assert!(list[6] == 91);
}

/// Test merging two unequal-sized vectors.
#[test]
fn lo_unsorted_multiple() {
    let mut list = vec![17, 20, 40, 80, 21, 32, 91];
    merge(&mut list, 4);
    assert!(list[0] == 17);
    assert!(list[1] == 20);
    assert!(list[2] == 21);
    assert!(list[3] == 32);
    assert!(list[4] == 40);
    assert!(list[5] == 80);
    assert!(list[6] == 91);
}

/// Test panic safety when the first run is longest
#[test]
fn lo_panic() {
    use std::panic::{catch_unwind, AssertUnwindSafe};

    let mut list = vec![1usize, 2, 3, 4, 5];

    catch_unwind(AssertUnwindSafe(|| {
        super::merge(
            &mut list,
            3,
            &comparator(|_, _| panic!("Expected panic: this is normal")),
        )
        .unwrap_or_else(never)
    }))
    .err()
    .unwrap();

    assert!(list[0] == 1);
    assert!(list[1] == 2);
    assert!(list[2] == 3);
    assert!(list[3] == 4);
    assert!(list[4] == 5);
}

/// Test panic safety when the second run is longest
#[test]
fn hi_panic() {
    use std::panic::{catch_unwind, AssertUnwindSafe};

    let mut list = vec![1usize, 2, 3, 4, 5];

    catch_unwind(AssertUnwindSafe(|| {
        super::merge(
            &mut list,
            2,
            &comparator(|_, _| panic!("Expected panic: this is normal")),
        )
        .unwrap_or_else(never)
    }))
    .err()
    .unwrap();

    assert!(list[0] == 1);
    assert!(list[1] == 2);
    assert!(list[2] == 3);
    assert!(list[3] == 4);
    assert!(list[4] == 5);
}

/// Test that the drop() is never run while sorting.

#[derive(Debug, PartialOrd, Ord, PartialEq, Eq)]
struct ExplodeOnDrop(usize);
impl Drop for ExplodeOnDrop {
    fn drop(&mut self) {
        panic!("We're not supposed to panic.");
    }
}

#[test]
fn lo_nodrop() {
    let mut list = vec![ExplodeOnDrop(3), ExplodeOnDrop(7), ExplodeOnDrop(2)];
    merge(&mut list, 2);
    assert!(list[0].0 == 2);
    assert!(list[1].0 == 3);
    assert!(list[2].0 == 7);
    list.into_iter().for_each(std::mem::forget);
}

#[test]
fn hi_nodrop() {
    let mut list = vec![ExplodeOnDrop(3), ExplodeOnDrop(2), ExplodeOnDrop(7)];
    merge(&mut list, 1);
    assert!(list[0].0 == 2);
    assert!(list[1].0 == 3);
    assert!(list[2].0 == 7);
    list.into_iter().for_each(std::mem::forget);
}

/// Ensure that, when we enter galloping mode, we still work right.

#[test]
fn lo_gallop_stress() {
    let mut list = vec![
        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 11, 12, 13, 14,
        15, 16, 17, 18, 19, 20,
    ];
    merge(&mut list, 21);
    assert!(list[0] == 1);
    assert!(list[1] == 2);
    assert!(list[2] == 3);
    assert!(list[3] == 4);
    assert!(list[4] == 5);
    assert!(list[5] == 6);
    assert!(list[6] == 7);
    assert!(list[7] == 8);
    assert!(list[8] == 9);
    assert!(list[9] == 10);
    assert!(list[10] == 11);
    assert!(list[11] == 12);
    assert!(list[12] == 13);
    assert!(list[13] == 14);
    assert!(list[14] == 15);
    assert!(list[15] == 16);
    assert!(list[16] == 17);
    assert!(list[17] == 18);
    assert!(list[18] == 19);
    assert!(list[19] == 20);
    assert!(list[20] == 20);
    assert!(list[21] == 21);
    assert!(list[22] == 22);
    assert!(list[23] == 23);
    assert!(list[24] == 24);
    assert!(list[25] == 25);
    assert!(list[26] == 26);
    assert!(list[27] == 27);
    assert!(list[28] == 28);
    assert!(list[29] == 29);
    assert!(list[30] == 30);
}

/// Ensure that, when we enter galloping mode, we still work right.

#[test]
fn hi_gallop_stress() {
    let mut list = vec![
        11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 21, 22, 23, 24,
        25, 26, 27, 28, 29, 30,
    ];
    merge(&mut list, 10);
    assert!(list[0] == 1);
    assert!(list[1] == 2);
    assert!(list[2] == 3);
    assert!(list[3] == 4);
    assert!(list[4] == 5);
    assert!(list[5] == 6);
    assert!(list[6] == 7);
    assert!(list[7] == 8);
    assert!(list[8] == 9);
    assert!(list[9] == 10);
    assert!(list[10] == 11);
    assert!(list[11] == 12);
    assert!(list[12] == 13);
    assert!(list[13] == 14);
    assert!(list[14] == 15);
    assert!(list[15] == 16);
    assert!(list[16] == 17);
    assert!(list[17] == 18);
    assert!(list[18] == 19);
    assert!(list[19] == 20);
    assert!(list[20] == 20);
    assert!(list[21] == 21);
    assert!(list[22] == 22);
    assert!(list[23] == 23);
    assert!(list[24] == 24);
    assert!(list[25] == 25);
    assert!(list[26] == 26);
    assert!(list[27] == 27);
    assert!(list[28] == 28);
    assert!(list[29] == 29);
    assert!(list[30] == 30);
}

/// Merge convenience used for tests.
fn merge<T: Ord>(list: &mut [T], first_len: usize) {
    super::merge(list, first_len, &ord_t_comparator()).unwrap_or_else(never)
}