defmodule Exercise do
  def string_ex1 do
    word = "had we but world enough, and time"
    String.split(word, ~r{,}, parts: 2)
    String.codepoints(word)
    String.reverse(word)
    String.to_charlist(word)
    counter_word = "had we but bacon enough, and treacle"
    String.myers_difference(word, counter_word)
  end

  def string_ex2 do
    IO.puts("today we are: #{Time.utc_now()}")
    IO.puts(~s<today we are: #{Time.utc_now()}>)
    word = ~w[now is the time]
    IO.inspect(word)
    IO.inspect(~W/now is the time/)
  end

  def regex_ex do
    word = IO.gets("enter any word: ") |> String.trim()
    IO.puts("does it match:  #{word =~ ~r/a.c/}")
    "cat has pooped on my cat paper" |> String.replace(~r/cat/, "dog", global: false) |> IO.puts()
    "cat has pooped on my cat paper" |> String.replace(~r/cat/, "dog") |> IO.puts()
  end

  def playing_around(t = {a, b}) do
    IO.puts("a=#{a}, b=#{b}")
    IO.puts(is_tuple(t))
  end

  def swap_tups({a, b}) do
    {b, a}
  end

  def check_match(a, a) do
    true
  end

  def len([]) do
    0
  end

  def len([_ | t]) do
    1 + len(t)
  end

  def sum([]) do
    0
  end

  def sum([h | t]) do
    h + sum(t)
  end

  def square([]) do
    []
  end

  def square([h | t]) do
    [h * h | square(t)]
  end

  def map([], _fn) do
    []
  end

  def map([h | t], fun) do
    [fun.(h) | map(t, fun)]
  end

  def check_match(_, _) do
    false
  end

  def sum_pairs([]) do
    []
  end

  def sum_pairs([h, h1 | t]) do
    [h + h1 | sum_pairs(t)]
  end

  def even_length([]) do
    true
  end

  def even_length([_h | t]) do
    !even_length(t)
  end

  def understand_rec([]) do
    0
  end

  def understand_rec([_head | tail]) do
    understand_rec(tail) + 1
  end
end