# Elixir does not recognize a varibale and extends it as a function. Why does this happen?

Here is my code:

``````defmodule HW3A do
def onepad(int, n \\ 0, list \\ []) do
case n do
^int -> list
_ -> onepad(int, n + 1, list ++ [:rand.uniform(int)])
end
end

defp string_to_num(string_grahemes, alphabets, cipher_nums, num_list \\ []) do
string_to_num(tl(string_grahemes), alphabets, tl(cipher_nums), [(Keyword.get(alphabets, hd(string_grahemes) |> String.to_atom)) + hd(cipher_nums) | num_list])
end

defp string_to_num([], alphabets, cipher_nums, num_list) do
num_list
end

def cipher(string) do
alphabets = Enum.zip([:a,:b,:c,:d,:e,:f,:g,:h,:i,:j,:k,:l,:m,:n,:o,:p,:q,:r,:s,:t,:u,:v,:w,:x,:y,:z], [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26])
string_num = []

encrypted_numbers = string_num(String.graphemes(string), alphabets, numbers, num_list)

IO.inspect(encrypted_numbers)
end
end
``````

When I call the function I get the following error:

``````warning: function string_to_num/4 is unused
practice.exs:113

** (CompileError) practice.exs:127: undefined function num_list/0
(elixir 1.12.2) src/elixir_locals.erl:114: anonymous fn/3 in :elixir_locals.ensure_no_undefined_local/3
practice.exs:105: (file)

``````

What am I doing wrong here ? I just want to return the argument.

Can you post the rest of your module? I’m pretty sure that the problem originates elsewhere, as the following compiles (with a bunch of warnings):

``````defmodule Example do
defp string_to_num(string_grahemes, alphabets, cipher_nums, num_list \\ []) do
string_to_num(tl(string_grahemes), alphabets, tl(cipher_nums), [(Keyword.get(alphabets, hd(string_grahemes) |> String.to_atom)) + hd(cipher_nums) | num_list])
end

defp string_to_num([], alphabets, cipher_nums, num_list) do
num_list
end
end
``````
3 Likes

I edited the post and the whole module is in the post now.

Not an exact answer, but you should probably swap the functions (put the last one before the first) because now `string_to_num` with an empty list as the first argument will be processed by the first function, where I think you would like it to use the second function.

2 Likes

Here you call `string_num` and use `num_list` as a parameter. Since such a variable does not exist in the scope of the `cipher` function, the compiler looks for a function but of course it does not exist as well.

4 Likes

As @zwippie suggests, you need to put the `string_to_num/4` with the `[]` first param first, since if the first param is `[]`, the first clause will match, with `[]` being assigned to `string_grahemes`. You should then be getting a compiler warning to that effect.

You should also be getting a compiler warning:

``````warning: defp string_to_num/4 has multiple clauses and also declares default values. In such cases, the default values should be defined in a header. Instead of:

def foo(:first_clause, b \\ :default) do ... end
def foo(:second_clause, b) do ... end

one should write:

def foo(a, b \\ :default)
def foo(:first_clause, b) do ... end
def foo(:second_clause, b) do ... end
``````
1 Like