stack! doesn't work properly

[HyeokSuLee]

example

  let a = array![[9., 7.], [5., 2.]];

  let b = array![[1., 9.], [5., 1.]];
  
  println!("a vstack b = \n{:?}\n", stack![Axis(0), a, b]);
  
  println!("a hstack b = \n{:?}\n", stack![Axis(1), a, b]);

should be

a vstack b = 
[[9.0, 7.0],
 [5.0, 2.0],
 [1.0, 9.0],
 [5.0, 1.0]], shape=[4, 2], strides=[2, 1], layout=C (0x1), const ndim=2

a hstack b = 
[[9.0, 7.0, 1.0, 9.0],
 [5.0, 2.0, 5.0, 1.0]], shape=[2, 4], strides=[4, 1], layout=C (0x1), const ndim=2

but it returns

a vstack b =
[[[9.0, 7.0],
  [5.0, 2.0]],

 [[1.0, 9.0],
  [5.0, 1.0]]], shape=[2, 2, 2], strides=[4, 2, 1], layout=Cc (0x5), const ndim=3

a hstack b =
[[[9.0, 7.0],
  [1.0, 9.0]],

 [[5.0, 2.0],
  [5.0, 1.0]]], shape=[2, 2, 2], strides=[2, 4, 1], layout=c (0x4), const ndim=3

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&code=%0D%0A%20%20use%20ndarray%3A%3Aprelude%3A%3A*%3B%0D%0A%20%20use%20ndarray%3A%3A%7BArray%2C%20Axis%2C%20stack%7D%3B%0D%0A%20%20%0D%0A%20%20fn%20main()%7B%0D%0A%20%20%20%20%20%20let%20a%20%3D%20array!%5B%5B9.%2C%207.%5D%2C%20%5B5.%2C%202.%5D%5D%3B%0D%0A%0D%0A%20%20%20%20%20%20let%20b%20%3D%20array!%5B%5B1.%2C%209.%5D%2C%20%5B5.%2C%201.%5D%5D%3B%0D%0A%20%20%20%20%20%20%0D%0A%20%20%20%20%20%20println!(%22a%20vstack%20b%20%3D%20%5Cn%7B%3A%3F%7D%5Cn%22%2C%20stack!%5BAxis(0)%2C%20a%2C%20b%5D)%3B%0D%0A%20%20%20%20%20%20%0D%0A%20%20%20%20%20%20println!(%22a%20hstack%20b%20%3D%20%5Cn%7B%3A%3F%7D%5Cn%22%2C%20stack!%5BAxis(1)%2C%20a%2C%20b%5D)%3B%0D%0A%20%20%7D

[jturner314]

The concatenate! macro does what you're looking for. (Playground) concatenate! concatenates arrays along an existing axis; stack! stacks arrays along a new axis.

[HyeokSuLee]

Great. But then, i think quick start tutorial need to be fixed.
/~https://github.com/rust-ndarray/ndarray/blob/master/README-quick-start.md

[jturner314]

Oh, good catch. Thanks! I've created #1156 to fix the quick start tutorial.