rever number

reverse.erl

-module(reverse).
-export([reverse/1]).

%% @doc reverse a number
-spec(reverse(number() | string() | atom()) -> string()).
reverse(ANumber) ->
	%% convert the number to an string
	Nmbr = string:reverse(atom_to_list(ANumber)),

	Check = not_a_number(Nmbr),

	if 
		Check == true -> erro;
		Check == false -> Nmbr
	end.


%% @doc verify if it's a number
-spec(not_a_number(number() | string() | atom()) -> atom()).
not_a_number(Nmbr) when is_number(Nmbr) ->
	true;

not_a_number(Nmbr) when is_list(Nmbr) -> 
	erro;

not_a_number(_) ->
	erro.

reverse_SUITE.erl

-module(reverse_SUITE).
-export([all/0]).
-import(reverse, [reverse/1]).
-include_lib("eunit/include/eunit.hrl").

all() -> [reverse_test].

reverse_test() ->
	[?_assert(reverse(1234) =:= 4321),
	?_assert(reverse(12) =:= 21),
	?_assert(reverse(6641112222223333333345678901118) =:= 8111098765433333333222222111466),
	?_assert(reverse("lala") =:= error)
	].