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use array_trait::Array;
use slice_ops::AsSlice;
use crate::private;
use super::ArrayTransposeAssign;
#[const_trait]
pub trait ArrayTranspose<T, const M: usize, const N: usize>: Array + AsSlice<Item = [T; N]>
{
/// Transposes a two-dimensional array (as if it were a matrix)
///
/// # Example
///
/// ```rust
/// use array__ops::ops::*;
///
/// let matrix: [[u8; 5]; 3] = [
/// [1, 2, 3, 4, 5],
/// [6, 7, 8, 9, 10],
/// [11, 12, 13, 14, 15]
/// ];
///
/// assert_eq!(matrix.transpose(), [
/// [1, 6, 11],
/// [2, 7, 12],
/// [3, 8, 13],
/// [4, 9, 14],
/// [5, 10, 15]
/// ]);
/// ```
fn transpose(self) -> [[T; M]; N];
}
impl<T, const M: usize, const N: usize> const ArrayTranspose<T, M, N> for [[T; N]; M]
{
fn transpose(self) -> [[T; M]; N]
{
// Transposes in-place
// Even though the matrices have different dimensions, they have equal size, which makes this trick possible.
let mut transposed = unsafe {
private::transmute(self)
};
if N == M
{
let square = unsafe {
(&mut transposed as *mut [[T; M]; N]).cast::<[[T; N]; N]>().as_mut_unchecked()
};
square.transpose_assign();
return transposed
}
let ptr = transposed[0].as_mut_ptr();
let m = unsafe {
core::slice::from_raw_parts_mut(ptr, M * N)
};
let mut visited = [[false; N]; M];
let visited = unsafe {
core::slice::from_raw_parts_mut(visited[0].as_mut_ptr(), M * N)
};
let mut c = 0;
while c < M * N
{
if !visited[c]
{
let mut a = c;
loop
{
a = if a == N * M - 1
{
N * M - 1
}
else
{
(M * a) % (N * M - 1)
};
visited[a] = true;
if a == c
{
break
}
unsafe {
m.swap_unchecked(a, c);
}
}
}
c += 1
}
transposed
}
}
#[cfg(test)]
mod test
{
use super::ArrayTranspose;
#[test]
fn transpose()
{
let a = [
[1, 2, 3],
[4, 5, 6]
];
let a_t = a.transpose();
println!("{:?}", a_t);
assert_eq!(
a_t,
[
[1, 4],
[2, 5],
[3, 6]
]
);
}
}