How can I create a function with all permutations of all digits up to the number of permutations asked?

[super_user]

I wish to create all permutations of all digits from a function.

For e.g. I have the array [1,2,3].
I would like the function to first print all possible permutations of 1 digit numbers:

1
2
3

then all possible permutations of 2-digit numbers(duplicates like 11, 22, 33 included)

11
12
13
21
22
23
31
32
33

and similarly for the 3 digit numbers.

I want to include all sort of possible permutations(11, 111, 222 etc.) up to the number of digits in the array, like in this example, I would like to have all permutations up to 3 digits.
How can I write it?

[H2CO3]

You can use multi_cartesian_product() from the itertools crate:

fn variations_up_to_length<T>(items: &[T]) -> impl Iterator<Item = Vec<&T>> {
    (1..=items.len()).flat_map(|n| {
        std::iter::repeat(items.iter()).take(n).multi_cartesian_product()
    })
}

(Playground)

By the way, these are not called permutations. These are called variations with repetition or Cartesian product or set-theoretic direct product.

[super_user]

Can I obtain such a result when the elements in the set are not integers, will it work for char or & str?
@H2CO3

[steffahn]

@super_user

will it work for char or & str ?

Just try it, I guess? The answer is yes

[H2CO3]

The implementation is generic.

[super_user]

thanks