rust/src/libcore/tests/slice.rs

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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
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use core::result::Result::{Ok, Err};
#[test]
fn test_position() {
let b = [1, 2, 3, 5, 5];
assert!(b.iter().position(|&v| v == 9) == None);
assert!(b.iter().position(|&v| v == 5) == Some(3));
assert!(b.iter().position(|&v| v == 3) == Some(2));
assert!(b.iter().position(|&v| v == 0) == None);
}
#[test]
fn test_rposition() {
let b = [1, 2, 3, 5, 5];
assert!(b.iter().rposition(|&v| v == 9) == None);
assert!(b.iter().rposition(|&v| v == 5) == Some(4));
assert!(b.iter().rposition(|&v| v == 3) == Some(2));
assert!(b.iter().rposition(|&v| v == 0) == None);
}
#[test]
fn test_binary_search() {
let b: [i32; 0] = [];
assert_eq!(b.binary_search(&5), Err(0));
let b = [4];
assert_eq!(b.binary_search(&3), Err(0));
assert_eq!(b.binary_search(&4), Ok(0));
assert_eq!(b.binary_search(&5), Err(1));
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let b = [1, 2, 4, 6, 8, 9];
assert_eq!(b.binary_search(&5), Err(3));
assert_eq!(b.binary_search(&6), Ok(3));
assert_eq!(b.binary_search(&7), Err(4));
assert_eq!(b.binary_search(&8), Ok(4));
let b = [1, 2, 4, 5, 6, 8];
assert_eq!(b.binary_search(&9), Err(6));
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let b = [1, 2, 4, 6, 7, 8, 9];
assert_eq!(b.binary_search(&6), Ok(3));
assert_eq!(b.binary_search(&5), Err(3));
assert_eq!(b.binary_search(&8), Ok(5));
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let b = [1, 2, 4, 5, 6, 8, 9];
assert_eq!(b.binary_search(&7), Err(5));
assert_eq!(b.binary_search(&0), Err(0));
let b = [1, 3, 3, 3, 7];
assert_eq!(b.binary_search(&0), Err(0));
assert_eq!(b.binary_search(&1), Ok(0));
assert_eq!(b.binary_search(&2), Err(1));
assert!(match b.binary_search(&3) { Ok(1...3) => true, _ => false });
assert!(match b.binary_search(&3) { Ok(1...3) => true, _ => false });
assert_eq!(b.binary_search(&4), Err(4));
assert_eq!(b.binary_search(&5), Err(4));
assert_eq!(b.binary_search(&6), Err(4));
assert_eq!(b.binary_search(&7), Ok(4));
assert_eq!(b.binary_search(&8), Err(5));
}
#[test]
// Test implementation specific behavior when finding equivalent elements.
// It is ok to break this test but when you do a crater run is highly advisable.
fn test_binary_search_implementation_details() {
let b = [1, 1, 2, 2, 3, 3, 3];
assert_eq!(b.binary_search(&1), Ok(1));
assert_eq!(b.binary_search(&2), Ok(3));
assert_eq!(b.binary_search(&3), Ok(6));
let b = [1, 1, 1, 1, 1, 3, 3, 3, 3];
assert_eq!(b.binary_search(&1), Ok(4));
assert_eq!(b.binary_search(&3), Ok(8));
let b = [1, 1, 1, 1, 3, 3, 3, 3, 3];
assert_eq!(b.binary_search(&1), Ok(3));
assert_eq!(b.binary_search(&3), Ok(8));
}
#[test]
fn test_iterator_nth() {
let v: &[_] = &[0, 1, 2, 3, 4];
for i in 0..v.len() {
assert_eq!(v.iter().nth(i).unwrap(), &v[i]);
}
assert_eq!(v.iter().nth(v.len()), None);
let mut iter = v.iter();
assert_eq!(iter.nth(2).unwrap(), &v[2]);
assert_eq!(iter.nth(1).unwrap(), &v[4]);
}
#[test]
fn test_iterator_last() {
let v: &[_] = &[0, 1, 2, 3, 4];
assert_eq!(v.iter().last().unwrap(), &4);
assert_eq!(v[..1].iter().last().unwrap(), &0);
}
#[test]
fn test_iterator_count() {
let v: &[_] = &[0, 1, 2, 3, 4];
assert_eq!(v.iter().count(), 5);
let mut iter2 = v.iter();
iter2.next();
iter2.next();
assert_eq!(iter2.count(), 3);
}
#[test]
fn test_chunks_count() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let c = v.chunks(3);
assert_eq!(c.count(), 2);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let c2 = v2.chunks(2);
assert_eq!(c2.count(), 3);
let v3: &[i32] = &[];
let c3 = v3.chunks(2);
assert_eq!(c3.count(), 0);
}
#[test]
fn test_chunks_nth() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let mut c = v.chunks(2);
assert_eq!(c.nth(1).unwrap(), &[2, 3]);
assert_eq!(c.next().unwrap(), &[4, 5]);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let mut c2 = v2.chunks(3);
assert_eq!(c2.nth(1).unwrap(), &[3, 4]);
assert_eq!(c2.next(), None);
}
#[test]
fn test_chunks_last() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let c = v.chunks(2);
assert_eq!(c.last().unwrap()[1], 5);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let c2 = v2.chunks(2);
assert_eq!(c2.last().unwrap()[0], 4);
}
#[test]
fn test_chunks_zip() {
let v1: &[i32] = &[0, 1, 2, 3, 4];
let v2: &[i32] = &[6, 7, 8, 9, 10];
let res = v1.chunks(2)
.zip(v2.chunks(2))
.map(|(a, b)| a.iter().sum::<i32>() + b.iter().sum::<i32>())
.collect::<Vec<_>>();
assert_eq!(res, vec![14, 22, 14]);
}
#[test]
fn test_chunks_mut_count() {
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let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
let c = v.chunks_mut(3);
assert_eq!(c.count(), 2);
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let v2: &mut [i32] = &mut [0, 1, 2, 3, 4];
let c2 = v2.chunks_mut(2);
assert_eq!(c2.count(), 3);
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let v3: &mut [i32] = &mut [];
let c3 = v3.chunks_mut(2);
assert_eq!(c3.count(), 0);
}
#[test]
fn test_chunks_mut_nth() {
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let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
let mut c = v.chunks_mut(2);
assert_eq!(c.nth(1).unwrap(), &[2, 3]);
assert_eq!(c.next().unwrap(), &[4, 5]);
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let v2: &mut [i32] = &mut [0, 1, 2, 3, 4];
let mut c2 = v2.chunks_mut(3);
assert_eq!(c2.nth(1).unwrap(), &[3, 4]);
assert_eq!(c2.next(), None);
}
#[test]
fn test_chunks_mut_last() {
let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
let c = v.chunks_mut(2);
assert_eq!(c.last().unwrap(), &[4, 5]);
let v2: &mut [i32] = &mut [0, 1, 2, 3, 4];
let c2 = v2.chunks_mut(2);
assert_eq!(c2.last().unwrap(), &[4]);
}
#[test]
fn test_chunks_mut_zip() {
let v1: &mut [i32] = &mut [0, 1, 2, 3, 4];
let v2: &[i32] = &[6, 7, 8, 9, 10];
for (a, b) in v1.chunks_mut(2).zip(v2.chunks(2)) {
let sum = b.iter().sum::<i32>();
for v in a {
*v += sum;
}
}
assert_eq!(v1, [13, 14, 19, 20, 14]);
}
#[test]
fn test_exact_chunks_count() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let c = v.exact_chunks(3);
assert_eq!(c.count(), 2);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let c2 = v2.exact_chunks(2);
assert_eq!(c2.count(), 2);
let v3: &[i32] = &[];
let c3 = v3.exact_chunks(2);
assert_eq!(c3.count(), 0);
}
#[test]
fn test_exact_chunks_nth() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let mut c = v.exact_chunks(2);
assert_eq!(c.nth(1).unwrap(), &[2, 3]);
assert_eq!(c.next().unwrap(), &[4, 5]);
let v2: &[i32] = &[0, 1, 2, 3, 4, 5, 6];
let mut c2 = v2.exact_chunks(3);
assert_eq!(c2.nth(1).unwrap(), &[3, 4, 5]);
assert_eq!(c2.next(), None);
}
#[test]
fn test_exact_chunks_last() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let c = v.exact_chunks(2);
assert_eq!(c.last().unwrap(), &[4, 5]);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let c2 = v2.exact_chunks(2);
assert_eq!(c2.last().unwrap(), &[2, 3]);
}
#[test]
fn test_exact_chunks_zip() {
let v1: &[i32] = &[0, 1, 2, 3, 4];
let v2: &[i32] = &[6, 7, 8, 9, 10];
let res = v1.exact_chunks(2)
.zip(v2.exact_chunks(2))
.map(|(a, b)| a.iter().sum::<i32>() + b.iter().sum::<i32>())
.collect::<Vec<_>>();
assert_eq!(res, vec![14, 22]);
}
#[test]
fn test_exact_chunks_mut_count() {
let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
let c = v.exact_chunks_mut(3);
assert_eq!(c.count(), 2);
let v2: &mut [i32] = &mut [0, 1, 2, 3, 4];
let c2 = v2.exact_chunks_mut(2);
assert_eq!(c2.count(), 2);
let v3: &mut [i32] = &mut [];
let c3 = v3.exact_chunks_mut(2);
assert_eq!(c3.count(), 0);
}
#[test]
fn test_exact_chunks_mut_nth() {
let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
let mut c = v.exact_chunks_mut(2);
assert_eq!(c.nth(1).unwrap(), &[2, 3]);
assert_eq!(c.next().unwrap(), &[4, 5]);
let v2: &mut [i32] = &mut [0, 1, 2, 3, 4, 5, 6];
let mut c2 = v2.exact_chunks_mut(3);
assert_eq!(c2.nth(1).unwrap(), &[3, 4, 5]);
assert_eq!(c2.next(), None);
}
#[test]
fn test_exact_chunks_mut_last() {
let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
let c = v.exact_chunks_mut(2);
assert_eq!(c.last().unwrap(), &[4, 5]);
let v2: &mut [i32] = &mut [0, 1, 2, 3, 4];
let c2 = v2.exact_chunks_mut(2);
assert_eq!(c2.last().unwrap(), &[2, 3]);
}
#[test]
fn test_exact_chunks_mut_zip() {
let v1: &mut [i32] = &mut [0, 1, 2, 3, 4];
let v2: &[i32] = &[6, 7, 8, 9, 10];
for (a, b) in v1.exact_chunks_mut(2).zip(v2.exact_chunks(2)) {
let sum = b.iter().sum::<i32>();
for v in a {
*v += sum;
}
}
assert_eq!(v1, [13, 14, 19, 20, 4]);
}
#[test]
fn test_windows_count() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let c = v.windows(3);
assert_eq!(c.count(), 4);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let c2 = v2.windows(6);
assert_eq!(c2.count(), 0);
let v3: &[i32] = &[];
let c3 = v3.windows(2);
assert_eq!(c3.count(), 0);
}
#[test]
fn test_windows_nth() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let mut c = v.windows(2);
assert_eq!(c.nth(2).unwrap()[1], 3);
assert_eq!(c.next().unwrap()[0], 3);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let mut c2 = v2.windows(4);
assert_eq!(c2.nth(1).unwrap()[1], 2);
assert_eq!(c2.next(), None);
}
#[test]
fn test_windows_last() {
let v: &[i32] = &[0, 1, 2, 3, 4, 5];
let c = v.windows(2);
assert_eq!(c.last().unwrap()[1], 5);
let v2: &[i32] = &[0, 1, 2, 3, 4];
let c2 = v2.windows(2);
assert_eq!(c2.last().unwrap()[0], 3);
}
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#[test]
fn test_windows_zip() {
let v1: &[i32] = &[0, 1, 2, 3, 4];
let v2: &[i32] = &[6, 7, 8, 9, 10];
let res = v1.windows(2)
.zip(v2.windows(2))
.map(|(a, b)| a.iter().sum::<i32>() + b.iter().sum::<i32>())
.collect::<Vec<_>>();
assert_eq!(res, [14, 18, 22, 26]);
}
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// The current implementation of SliceIndex fails to handle methods
// orthogonally from range types; therefore, it is worth testing
// all of the indexing operations on each input.
mod slice_index {
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// This checks all six indexing methods, given an input range that
// should succeed. (it is NOT suitable for testing invalid inputs)
macro_rules! assert_range_eq {
($arr:expr, $range:expr, $expected:expr)
=> {
let mut arr = $arr;
let mut expected = $expected;
{
let s: &[_] = &arr;
let expected: &[_] = &expected;
assert_eq!(&s[$range], expected, "(in assertion for: index)");
assert_eq!(s.get($range), Some(expected), "(in assertion for: get)");
unsafe {
assert_eq!(
s.get_unchecked($range), expected,
"(in assertion for: get_unchecked)",
);
}
}
{
let s: &mut [_] = &mut arr;
let expected: &mut [_] = &mut expected;
assert_eq!(
&mut s[$range], expected,
"(in assertion for: index_mut)",
);
assert_eq!(
s.get_mut($range), Some(&mut expected[..]),
"(in assertion for: get_mut)",
);
unsafe {
assert_eq!(
s.get_unchecked_mut($range), expected,
"(in assertion for: get_unchecked_mut)",
);
}
}
}
}
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// Make sure the macro can actually detect bugs,
// because if it can't, then what are we even doing here?
//
// (Be aware this only demonstrates the ability to detect bugs
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// in the FIRST method that panics, as the macro is not designed
// to be used in `should_panic`)
#[test]
#[should_panic(expected = "out of range")]
fn assert_range_eq_can_fail_by_panic() {
assert_range_eq!([0, 1, 2], 0..5, [0, 1, 2]);
}
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// (Be aware this only demonstrates the ability to detect bugs
// in the FIRST method it calls, as the macro is not designed
// to be used in `should_panic`)
#[test]
#[should_panic(expected = "==")]
fn assert_range_eq_can_fail_by_inequality() {
assert_range_eq!([0, 1, 2], 0..2, [0, 1, 2]);
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}
// Test cases for bad index operations.
//
// This generates `should_panic` test cases for Index/IndexMut
// and `None` test cases for get/get_mut.
macro_rules! panic_cases {
($(
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// each test case needs a unique name to namespace the tests
in mod $case_name:ident {
data: $data:expr;
// optional:
//
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// one or more similar inputs for which data[input] succeeds,
// and the corresponding output as an array. This helps validate
// "critical points" where an input range straddles the boundary
// between valid and invalid.
// (such as the input `len..len`, which is just barely valid)
$(
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good: data[$good:expr] == $output:expr;
)*
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bad: data[$bad:expr];
message: $expect_msg:expr;
}
)*) => {$(
mod $case_name {
#[test]
fn pass() {
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let mut v = $data;
$( assert_range_eq!($data, $good, $output); )*
{
let v: &[_] = &v;
assert_eq!(v.get($bad), None, "(in None assertion for get)");
}
{
let v: &mut [_] = &mut v;
assert_eq!(v.get_mut($bad), None, "(in None assertion for get_mut)");
}
}
#[test]
#[should_panic(expected = $expect_msg)]
fn index_fail() {
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let v = $data;
let v: &[_] = &v;
let _v = &v[$bad];
}
#[test]
#[should_panic(expected = $expect_msg)]
fn index_mut_fail() {
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let mut v = $data;
let v: &mut [_] = &mut v;
let _v = &mut v[$bad];
}
}
)*};
}
#[test]
fn simple() {
let v = [0, 1, 2, 3, 4, 5];
assert_range_eq!(v, .., [0, 1, 2, 3, 4, 5]);
assert_range_eq!(v, ..2, [0, 1]);
assert_range_eq!(v, ..=1, [0, 1]);
assert_range_eq!(v, 2.., [2, 3, 4, 5]);
assert_range_eq!(v, 1..4, [1, 2, 3]);
assert_range_eq!(v, 1..=3, [1, 2, 3]);
}
panic_cases! {
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in mod rangefrom_len {
data: [0, 1, 2, 3, 4, 5];
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good: data[6..] == [];
bad: data[7..];
message: "but ends at"; // perhaps not ideal
}
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in mod rangeto_len {
data: [0, 1, 2, 3, 4, 5];
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good: data[..6] == [0, 1, 2, 3, 4, 5];
bad: data[..7];
message: "out of range";
}
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in mod rangetoinclusive_len {
data: [0, 1, 2, 3, 4, 5];
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good: data[..=5] == [0, 1, 2, 3, 4, 5];
bad: data[..=6];
message: "out of range";
}
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in mod range_len_len {
data: [0, 1, 2, 3, 4, 5];
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good: data[6..6] == [];
bad: data[7..7];
message: "out of range";
}
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in mod rangeinclusive_len_len {
data: [0, 1, 2, 3, 4, 5];
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good: data[6..=5] == [];
bad: data[7..=6];
message: "out of range";
}
}
panic_cases! {
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in mod range_neg_width {
data: [0, 1, 2, 3, 4, 5];
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good: data[4..4] == [];
bad: data[4..3];
message: "but ends at";
}
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in mod rangeinclusive_neg_width {
data: [0, 1, 2, 3, 4, 5];
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good: data[4..=3] == [];
bad: data[4..=2];
message: "but ends at";
}
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}
panic_cases! {
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in mod rangeinclusive_overflow {
data: [0, 1];
// note: using 0 specifically ensures that the result of overflowing is 0..0,
// so that `get` doesn't simply return None for the wrong reason.
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bad: data[0 ..= ::std::usize::MAX];
message: "maximum usize";
}
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in mod rangetoinclusive_overflow {
data: [0, 1];
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bad: data[..= ::std::usize::MAX];
message: "maximum usize";
}
} // panic_cases!
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}
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#[test]
fn test_find_rfind() {
let v = [0, 1, 2, 3, 4, 5];
let mut iter = v.iter();
let mut i = v.len();
while let Some(&elt) = iter.rfind(|_| true) {
i -= 1;
assert_eq!(elt, v[i]);
}
assert_eq!(i, 0);
assert_eq!(v.iter().rfind(|&&x| x <= 3), Some(&3));
}
#[test]
fn test_iter_folds() {
let a = [1, 2, 3, 4, 5]; // len>4 so the unroll is used
assert_eq!(a.iter().fold(0, |acc, &x| 2*acc + x), 57);
assert_eq!(a.iter().rfold(0, |acc, &x| 2*acc + x), 129);
let fold = |acc: i32, &x| acc.checked_mul(2)?.checked_add(x);
assert_eq!(a.iter().try_fold(0, &fold), Some(57));
assert_eq!(a.iter().try_rfold(0, &fold), Some(129));
// short-circuiting try_fold, through other methods
let a = [0, 1, 2, 3, 5, 5, 5, 7, 8, 9];
let mut iter = a.iter();
assert_eq!(iter.position(|&x| x == 3), Some(3));
assert_eq!(iter.rfind(|&&x| x == 5), Some(&5));
assert_eq!(iter.len(), 2);
}
#[test]
Deprecate [T]::rotate in favor of [T]::rotate_{left,right}. Background ========== Slices currently have an unstable [`rotate`] method which rotates elements in the slice to the _left_ N positions. [Here][tracking] is the tracking issue for this unstable feature. ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); ``` Proposal ======== Deprecate the [`rotate`] method and introduce `rotate_left` and `rotate_right` methods. ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate_left(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); ``` ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate_right(2); assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']); ``` Justification ============= I used this method today for my first time and (probably because I’m a naive westerner who reads LTR) was surprised when the docs mentioned that elements get rotated in a left-ward direction. I was in a situation where I needed to shift elements in a right-ward direction and had to context switch from the main problem I was working on and think how much to rotate left in order to accomplish the right-ward rotation I needed. Ruby’s `Array.rotate` shifts left-ward, Python’s `deque.rotate` shifts right-ward. Both of their implementations allow passing negative numbers to shift in the opposite direction respectively. Introducing `rotate_left` and `rotate_right` would: - remove ambiguity about direction (alleviating need to read docs 😉) - make it easier for people who need to rotate right [`rotate`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate [tracking]: https://github.com/rust-lang/rust/issues/41891
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fn test_rotate_left() {
const N: usize = 600;
let a: &mut [_] = &mut [0; N];
for i in 0..N {
a[i] = i;
}
Deprecate [T]::rotate in favor of [T]::rotate_{left,right}. Background ========== Slices currently have an unstable [`rotate`] method which rotates elements in the slice to the _left_ N positions. [Here][tracking] is the tracking issue for this unstable feature. ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); ``` Proposal ======== Deprecate the [`rotate`] method and introduce `rotate_left` and `rotate_right` methods. ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate_left(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); ``` ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate_right(2); assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']); ``` Justification ============= I used this method today for my first time and (probably because I’m a naive westerner who reads LTR) was surprised when the docs mentioned that elements get rotated in a left-ward direction. I was in a situation where I needed to shift elements in a right-ward direction and had to context switch from the main problem I was working on and think how much to rotate left in order to accomplish the right-ward rotation I needed. Ruby’s `Array.rotate` shifts left-ward, Python’s `deque.rotate` shifts right-ward. Both of their implementations allow passing negative numbers to shift in the opposite direction respectively. Introducing `rotate_left` and `rotate_right` would: - remove ambiguity about direction (alleviating need to read docs 😉) - make it easier for people who need to rotate right [`rotate`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate [tracking]: https://github.com/rust-lang/rust/issues/41891
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a.rotate_left(42);
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let k = N - 42;
for i in 0..N {
Deprecate [T]::rotate in favor of [T]::rotate_{left,right}. Background ========== Slices currently have an unstable [`rotate`] method which rotates elements in the slice to the _left_ N positions. [Here][tracking] is the tracking issue for this unstable feature. ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); ``` Proposal ======== Deprecate the [`rotate`] method and introduce `rotate_left` and `rotate_right` methods. ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate_left(2); assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); ``` ```rust let mut a = ['a', 'b' ,'c', 'd', 'e', 'f']; a.rotate_right(2); assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']); ``` Justification ============= I used this method today for my first time and (probably because I’m a naive westerner who reads LTR) was surprised when the docs mentioned that elements get rotated in a left-ward direction. I was in a situation where I needed to shift elements in a right-ward direction and had to context switch from the main problem I was working on and think how much to rotate left in order to accomplish the right-ward rotation I needed. Ruby’s `Array.rotate` shifts left-ward, Python’s `deque.rotate` shifts right-ward. Both of their implementations allow passing negative numbers to shift in the opposite direction respectively. Introducing `rotate_left` and `rotate_right` would: - remove ambiguity about direction (alleviating need to read docs 😉) - make it easier for people who need to rotate right [`rotate`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate [tracking]: https://github.com/rust-lang/rust/issues/41891
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assert_eq!(a[(i + k) % N], i);
}
}
#[test]
fn test_rotate_right() {
const N: usize = 600;
let a: &mut [_] = &mut [0; N];
for i in 0..N {
a[i] = i;
}
a.rotate_right(42);
for i in 0..N {
assert_eq!(a[(i + 42) % N], i);
}
}
#[test]
#[cfg(not(target_arch = "wasm32"))]
fn sort_unstable() {
use core::cmp::Ordering::{Equal, Greater, Less};
use core::slice::heapsort;
use rand::{Rng, XorShiftRng};
let mut v = [0; 600];
let mut tmp = [0; 600];
let mut rng = XorShiftRng::new_unseeded();
for len in (2..25).chain(500..510) {
let v = &mut v[0..len];
let tmp = &mut tmp[0..len];
for &modulus in &[5, 10, 100, 1000] {
for _ in 0..100 {
for i in 0..len {
v[i] = rng.gen::<i32>() % modulus;
}
// Sort in default order.
tmp.copy_from_slice(v);
tmp.sort_unstable();
assert!(tmp.windows(2).all(|w| w[0] <= w[1]));
// Sort in ascending order.
tmp.copy_from_slice(v);
tmp.sort_unstable_by(|a, b| a.cmp(b));
assert!(tmp.windows(2).all(|w| w[0] <= w[1]));
// Sort in descending order.
tmp.copy_from_slice(v);
tmp.sort_unstable_by(|a, b| b.cmp(a));
assert!(tmp.windows(2).all(|w| w[0] >= w[1]));
// Test heapsort using `<` operator.
tmp.copy_from_slice(v);
heapsort(tmp, |a, b| a < b);
assert!(tmp.windows(2).all(|w| w[0] <= w[1]));
// Test heapsort using `>` operator.
tmp.copy_from_slice(v);
heapsort(tmp, |a, b| a > b);
assert!(tmp.windows(2).all(|w| w[0] >= w[1]));
}
}
}
// Sort using a completely random comparison function.
// This will reorder the elements *somehow*, but won't panic.
for i in 0..v.len() {
v[i] = i as i32;
}
v.sort_unstable_by(|_, _| *rng.choose(&[Less, Equal, Greater]).unwrap());
v.sort_unstable();
for i in 0..v.len() {
assert_eq!(v[i], i as i32);
}
// Should not panic.
[0i32; 0].sort_unstable();
[(); 10].sort_unstable();
[(); 100].sort_unstable();
let mut v = [0xDEADBEEFu64];
v.sort_unstable();
assert!(v == [0xDEADBEEF]);
}
pub mod memchr {
use core::slice::memchr::{memchr, memrchr};
// test fallback implementations on all platforms
#[test]
fn matches_one() {
assert_eq!(Some(0), memchr(b'a', b"a"));
}
#[test]
fn matches_begin() {
assert_eq!(Some(0), memchr(b'a', b"aaaa"));
}
#[test]
fn matches_end() {
assert_eq!(Some(4), memchr(b'z', b"aaaaz"));
}
#[test]
fn matches_nul() {
assert_eq!(Some(4), memchr(b'\x00', b"aaaa\x00"));
}
#[test]
fn matches_past_nul() {
assert_eq!(Some(5), memchr(b'z', b"aaaa\x00z"));
}
#[test]
fn no_match_empty() {
assert_eq!(None, memchr(b'a', b""));
}
#[test]
fn no_match() {
assert_eq!(None, memchr(b'a', b"xyz"));
}
#[test]
fn matches_one_reversed() {
assert_eq!(Some(0), memrchr(b'a', b"a"));
}
#[test]
fn matches_begin_reversed() {
assert_eq!(Some(3), memrchr(b'a', b"aaaa"));
}
#[test]
fn matches_end_reversed() {
assert_eq!(Some(0), memrchr(b'z', b"zaaaa"));
}
#[test]
fn matches_nul_reversed() {
assert_eq!(Some(4), memrchr(b'\x00', b"aaaa\x00"));
}
#[test]
fn matches_past_nul_reversed() {
assert_eq!(Some(0), memrchr(b'z', b"z\x00aaaa"));
}
#[test]
fn no_match_empty_reversed() {
assert_eq!(None, memrchr(b'a', b""));
}
#[test]
fn no_match_reversed() {
assert_eq!(None, memrchr(b'a', b"xyz"));
}
#[test]
fn each_alignment_reversed() {
let mut data = [1u8; 64];
let needle = 2;
let pos = 40;
data[pos] = needle;
for start in 0..16 {
assert_eq!(Some(pos - start), memrchr(needle, &data[start..]));
}
}
}
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#[test]
fn test_align_to_simple() {
let bytes = [1u8, 2, 3, 4, 5, 6, 7];
let (prefix, aligned, suffix) = unsafe { bytes.align_to::<u16>() };
assert_eq!(aligned.len(), 3);
assert!(prefix == [1] || suffix == [7]);
let expect1 = [1 << 8 | 2, 3 << 8 | 4, 5 << 8 | 6];
let expect2 = [1 | 2 << 8, 3 | 4 << 8, 5 | 6 << 8];
let expect3 = [2 << 8 | 3, 4 << 8 | 5, 6 << 8 | 7];
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let expect4 = [2 | 3 << 8, 4 | 5 << 8, 6 | 7 << 8];
assert!(aligned == expect1 || aligned == expect2 || aligned == expect3 || aligned == expect4,
"aligned={:?} expected={:?} || {:?} || {:?} || {:?}",
aligned, expect1, expect2, expect3, expect4);
}
#[test]
fn test_align_to_zst() {
let bytes = [1, 2, 3, 4, 5, 6, 7];
let (prefix, aligned, suffix) = unsafe { bytes.align_to::<()>() };
assert_eq!(aligned.len(), 0);
assert!(prefix == [1, 2, 3, 4, 5, 6, 7] || suffix == [1, 2, 3, 4, 5, 6, 7]);
}
#[test]
fn test_align_to_non_trivial() {
#[repr(align(8))] struct U64(u64, u64);
#[repr(align(8))] struct U64U64U32(u64, u64, u32);
let data = [U64(1, 2), U64(3, 4), U64(5, 6), U64(7, 8), U64(9, 10), U64(11, 12), U64(13, 14),
U64(15, 16)];
let (prefix, aligned, suffix) = unsafe { data.align_to::<U64U64U32>() };
assert_eq!(aligned.len(), 4);
assert_eq!(prefix.len() + suffix.len(), 2);
}