I would like to write a function fn f<A>(xs: &mut [A; 9]) that reorders an array in-place from:
[a, b, c,
d, e, f,
g, h, i]
to:
[g, d, a,
h, e, b,
i, f, c]
I can't reassign the array due to moving elements out of array:
fn f1<A>(xs: &mut [A; 9]) {
*xs = [xs[6], xs[3], xs[0], xs[7], xs[4], xs[1], xs[8], xs[5], xs[2]];
}
error[E0508]: cannot move out of type `[A; 9]`, a non-copy array
--> src/lib.rs:2:12
|
2 | *xs = [xs[6], xs[3], xs[0], xs[7], xs[4], xs[1], xs[8], xs[5], xs[2]];
| ^^^^^
| |
| cannot move out of here
| move occurs because `xs[_]` has type `A`, which does not implement the `Copy` trait
I cannot do multiple mutable borrows:
fn f2<A>(xs: &mut [A; 9]) {
std::mem::swap(&mut xs[0], &mut xs[6]);
}
error[E0499]: cannot borrow `xs[_]` as mutable more than once at a time
--> src/lib.rs:2:32
|
2 | std::mem::swap(&mut xs[0], &mut xs[6]);
| -------------- ---------- ^^^^^^^^^^ second mutable borrow occurs here
| | |
| | first mutable borrow occurs here
| first borrow later used by call
There is no built-in function that does this transformation for me.
How to implement this?
