Solve the first part of day 3 puzzle

Author: rvprasad

day3/README.md

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+Execute this code via `elixir day3.exs <filename>`.
+
+### Observations
+
+1. Getting back into Elixir was easy.  Just like with Clojure :)

day3/day3.exs

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+defmodule Day3 do
+  def get_memory(filename) do
+    File.stream!(filename) |> Stream.map(&Function.identity/1) 
+  end 
+
+  def get_multiplicands1(line) do
+    Regex.scan(~r/mul\((\d{1,3}),(\d{1,3})\)/, line) |> Enum.map(&Enum.drop(&1, 1))
+  end
+
+  def get_result(filename, get_multiplicands) do
+    get_memory(filename)
+    |> Enum.map(get_multiplicands)
+    |> Enum.flat_map(&Function.identity/1)
+    |> Enum.map(fn pair -> Enum.map(pair, &Integer.parse(&1)) |> Enum.map(&elem(&1, 0)) end)
+    |> Enum.map(&Enum.product/1)
+    |> Enum.sum()
+  end
+end
+
+filename = System.argv() |> List.first()
+Day3.get_result(filename, &Day3.get_multiplicands1/1) |> IO.puts