reverse.cairo

func reverse{syscall_ptr : felt*, range_check_ptr, pedersen_ptr : HashBuiltin*}(
    arr_len : felt, arr : felt*
) -> (rev_arr_len : felt, rev_arr : felt*):

    # if our array is empty (i.e. we reached the end of our recursion)
    if arr_len == 0:
        let (rev_arr) = alloc()
        return (0, rev_arr)
    end

    # otherwise, we reverse the rest of our array
    let (rev_rest_len, rev_rest) = reverse(arr_len-1, arr+1)

    # and then we append the current element (the first of our array)
    # at the end of the reversed array
    assert rev_rest[rev_rest_len] = [arr]

    return (rev_rest_len+1, rev_rest)
end