Compare vec to some fixed arrays

1

I'm trying to compare a rotation matrix from a file to a few knows rotation matrices, like this:

struct RotationMatrix;
impl RotationMatrix {
	const NO_ROTATION: [u8; 36] = [
		0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x40, 0, 0, 0,
	];
	const ROTATION_90: [u8; 36] = [
		0, 0, 0, 0, 0, 0x01, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x40, 0,
		0, 0,
	];
	const ROTATION_180: [u8; 36] = [
		0xFF, 0xFF, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x40,
		0, 0, 0,
	];
	const ROTATION_270: [u8; 36] = [
		0, 0, 0, 0, 0xFF, 0xFF, 0, 0, 0, 0, 0, 0, 0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x40, 0,
		0, 0,
	];
}

let matrix_structure: Vec<u8> = file.read_to_end()?;
match data_from_file {
  RotationMatrix::NO_ROTATION => { println!("No rotation") },
  _ => println!("Some rotation"),
}

I get this:

  --> src\rotate.rs:77:3
   |
9  |       const NO_ROTATION: [u8; 36] = [
   |  _____-
10 | |         0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x40, 0, 0, 0,
11 | |     ];
   | |______- associated constant defined here
...
76 |       match matrix_structure {
   |             ---------------- this expression has type `Vec<u8>`
77 |           RotationMatrix::NO_ROTATION => println!("No rotation"),
   |           ^^^^^^^^^^^^^^^^-----------
   |           |               |
   |           |               help: introduce a new binding instead: `other_no_rotation`
   |           expected struct `Vec`, found array `[u8; 36]`
   |           `NO_ROTATION` is interpreted as an associated constant, not a new binding
   |
   = note: expected type `Vec<u8>`
             found array `[u8; 36]`

How can I make this work? Feel free to store the known rotation matrices in a different type, this was just the first idea I came up with.

2

Try match &*matrix_structure { RotationMatrix::NO_ROTATION => ... when using const NO_ROTATION: &[u8] = &[0, 0x01, ....

3

Makes no difference. (And shouldn't because of match ergonomics?)

4

This compiles:

struct RotationMatrix;
impl RotationMatrix {
	const NO_ROTATION: &'static [u8] = &[
		0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x40, 0, 0, 0,
	];
}

fn main() {
    let matrix_structure: Vec<u8> = todo!();
    match &*matrix_structure {
      RotationMatrix::NO_ROTATION => { println!("No rotation") },
      _ => println!("Some rotation"),
    }
}
5

Oh, you changed the type at the top as well, didn't see that. :see_no_evil: