danj3

defmodule ElmdbStage do
  @moduledoc """
  Create a GenStage for an :elmdb based LMDB database cursor.
  This is for linearly reading from a db
  """
  use GenStage

  def start_link( env, db ) do
    GenStage.start_link( __MODULE__, { env, db } )
  end

danj3

defmodule HashSignature do
  @doc """
    encode input to a sha256 and output as an armored string.
    results should be fully portable and consistent with other
    tools.
  """
  def get( input ) do
    :crypto.hash( :sha256, input )
    |> :crypto.bytes_to_integer
    |> (fn i -> :io_lib.format("~64.16.0b",[i]) |> hd end ).()

danj3

defmodule TimeAgent do

  def start_link do
    Agent.start_link( fn -> { Map.new, Map.new } end, name: __MODULE__ )
  end
  
  def time_run( m, f, a ) do
    { us, result } = :timer.tc( m, f, a )
    Agent.cast( __MODULE__, __MODULE__, :add_sample, [ to_string(m) <> "." <> to_string(f), us ] )
    result

danj3

defmodule TermRoundTrip do
  @moduledoc """
  Convert a term to a readable string then back to a term
  """

  def term_to_binary( term ) do
    :io_lib.format("~p.~n", [ term ] )
    |> :erlang.iolist_to_binary
  end

danj3

  defmodule Day4 do
    def parser( input ) do
      String.split( input, "\n" )
      |> Enum.reduce( [], fn "", acc -> acc; line,acc -> [ String.split(line," ") | acc ] end )
    end

    def start1( input ) do
      parser( input ) |> step1a( [valid: 0, invalid: 0] )
    end

danj3

  defmodule Day3 do
    # This does more work than required but is still O(1)
    # diagonal low right is even square root                                                           
    def start1( val ) do
      col_height = :math.sqrt( val ) |> Float.ceil |> trunc
      col_height = if Integer.mod( col_height, 2 ) == 0, do: col_height+1, else: col_height
      low_right_corner = :math.pow( col_height, 2 ) |> trunc
      distance = low_right_corner - val
      ring_length = col_height * 4 - 4

danj3

  defmodule Day2 do
    def parser( input ) do
      String.split( input, "\n" )
      |> Enum.map( fn k ->
        String.split( k, "\t")
        |> Enum.map( &String.to_integer/1 )
      end )
    end
    def start1( input ) do
      input

danj3

defmodule TimeoutExample do
 use GenServer
 def init(_args), do: {:ok, 0, 5_000}
 def handle_info(:timeout, state) do   
   IO.inspect(state)
   {:noreply, state+1, 5_000 + state*1000}
 end
end

iex> {:ok, p} = GenServer.start(TimeoutExample, [])