Add documentation

Author: sylph01

lib/random_string.ex

@@ -1,4 +1,8 @@
 defmodule RandomString do
+  @moduledoc """
+  An utility to generate random strings of desired character sets.
+  """
+
   @simple_classes %{
     # {base, number_of_chars}
     numeric:         {?0, 10},
@@ -9,15 +13,25 @@ defmodule RandomString do
 
   @misleading_chars '01258' ++ 'ijlouv' ++ 'BIOSUVZ'
 
+  @doc """
+  Take `n` characters from `:alphanumeric` class characters.
+  """
   # public APIs
   def take(n) when is_integer(n) do
     take(n, :alphanumeric)
   end
 
+  @doc """
+  Take `n` characters from a specified character class.
+  Available character classes are: `:alphabetical`, `:alphanumeric`, `:numeric`, `:lowercase`, `:uppercase`, `printable_chars`.
+  """
   def take(n, character_class) when is_integer(n) do
     stream(character_class) |> Enum.take(n) |> List.to_string
   end
 
+  @doc """
+  Take `n` characters from alphanumeric characters, excluding "misleading characters" (characters that look similar to another character: `01258ijlouvBIOSUVZ`).
+  """
   def take_without_misleading_characters(n) when is_integer(n) do
     stream_without_misleading_characters() |> Enum.take(n) |> List.to_string
   end
@@ -31,6 +45,9 @@ defmodule RandomString do
 
 
   # definition of streams
+  @doc """
+  Returns a [Stream](https://hexdocs.pm/elixir/Stream.html) of characters with a specified character class.
+  """
   def stream(character_class) when character_class in [:numeric, :uppercase, :lowercase, :printable_chars] do
     {base, number_of_chars} = @simple_classes[character_class]
     # :rand.uniform returns 1 <= X <= N
@@ -68,6 +85,9 @@ defmodule RandomString do
     stream(character_class) |> Stream.reject(fn x -> Enum.member?(@misleading_chars, x) end)
   end
 
+  @doc """
+  Returns a [Stream](https://hexdocs.pm/elixir/Stream.html) of characters that does not include characters specified in `character_list`.
+  """
   def stream_without_characters(character_list, character_class \\ :alphanumeric) when is_list(character_list) do
     stream(character_class) |> Stream.reject(fn x -> Enum.member?(character_list, x) end)
   end