 
   @doc """
   Works like `binary_to_atom` but the atom must exist.
+  Allowed in guard clauses.
 
   ## Examples
 

  @doc """
  Implements the unary operator ! as a macro. It receives any
  argument and returns true if it is false or nil. Returns false
  otherwise.

  ## Examples


  end

  @doc """
  Concatenates two binaries. Allowed in guard clauses.

  ## Examples

