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/// Threading utilities
pub mod thread {
/// Like `thread::spawn`, but with a `name` argument
pub fn spawn_named<F, T, S>(name: S, f: F) -> ::std::thread::JoinHandle<T>
where F: FnOnce() -> T,
F: Send + 'static,
T: Send + 'static,
S: Into<String>
{
::std::thread::Builder::new().name(name.into()).spawn(f).expect("thread spawn works")
}
}
/// Types that can have their elements rotated
pub trait Rotate {
fn rotate(&mut self, positions: isize);
}
impl<T> Rotate for [T] {
fn rotate(&mut self, positions: isize) {
// length is needed over and over
let len = self.len();
// Enforce positions in [0, len) and treat negative rotations as a
// posititive rotation of len - positions.
let positions = if positions > 0 {
positions as usize % len
} else {
len - (-positions as usize) % len
};
// If positions is 0 or the entire slice, it's a noop.
if positions == 0 || positions == len {
return;
}
self[..positions].reverse();
self[positions..].reverse();
self.reverse();
}
}
#[cfg(test)]
mod tests {
use super::Rotate;
#[test]
fn rotate_forwards_works() {
let s = &mut [1, 2, 3, 4, 5];
s.rotate(1);
assert_eq!(&[2, 3, 4, 5, 1], s);
}
#[test]
fn rotate_backwards_works() {
let s = &mut [1, 2, 3, 4, 5];
s.rotate(-1);
assert_eq!(&[5, 1, 2, 3, 4], s);
}
#[test]
fn rotate_multiple_forwards() {
let s = &mut [1, 2, 3, 4, 5, 6, 7];
s.rotate(2);
assert_eq!(&[3, 4, 5, 6, 7, 1, 2], s);
}
#[test]
fn rotate_multiple_backwards() {
let s = &mut [1, 2, 3, 4, 5];
s.rotate(-3);
assert_eq!(&[3, 4, 5, 1, 2], s);
}
#[test]
fn rotate_forwards_overflow() {
let s = &mut [1, 2, 3, 4, 5];
s.rotate(6);
assert_eq!(&[2, 3, 4, 5, 1], s);
}
#[test]
fn rotate_backwards_overflow() {
let s = &mut [1, 2, 3, 4, 5];
s.rotate(-6);
assert_eq!(&[5, 1, 2, 3, 4], s);
}
}
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