pop-count

elixir/pop-count/.exercism/config.json

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+{
+  "authors": [
+    "kahgoh"
+  ],
+  "files": {
+    "solution": [
+      "lib/pop_count.ex"
+    ],
+    "test": [
+      "test/pop_count_test.exs"
+    ],
+    "example": [
+      ".meta/example.ex"
+    ]
+  },
+  "blurb": "Help Eliud count the number of eggs in her chicken coop by counting the number of 1 bits in a binary representation.",
+  "source": "Christian Willner, Eric Willigers",
+  "source_url": "https://forum.exercism.org/t/new-exercise-suggestion-pop-count/7632/5"
+}

elixir/pop-count/.exercism/metadata.json

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+{"track":"elixir","exercise":"pop-count","id":"d2363c035a2748d9a3b9561ce18f0315","url":"https://exercism.org/tracks/elixir/exercises/pop-count","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/pop-count/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

elixir/pop-count/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+isogram-*.tar
+

elixir/pop-count/HELP.md

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+# Help
+
+## Running the tests
+
+From the terminal, change to the base directory of the exercise then execute the tests with:
+
+```bash
+$ mix test
+```
+
+This will execute the test file found in the `test` subfolder -- a file ending in `_test.exs`
+
+Documentation:
+
+* [`mix test` - Elixir's test execution tool](https://hexdocs.pm/mix/Mix.Tasks.Test.html)
+* [`ExUnit` - Elixir's unit test library](https://hexdocs.pm/ex_unit/ExUnit.html)
+
+## Pending tests
+
+In test suites of practice exercises, all but the first test have been tagged to be skipped.
+
+Once you get a test passing, you can unskip the next one by commenting out the relevant `@tag :pending` with a `#` symbol.
+
+For example:
+
+```elixir
+# @tag :pending
+test "shouting" do
+  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
+end
+```
+
+If you wish to run all tests at once, you can include all skipped test by using the `--include` flag on the `mix test` command:
+
+```bash
+$ mix test --include pending
+```
+
+Or, you can enable all the tests by commenting out the `ExUnit.configure` line in the file `test/test_helper.exs`.
+
+```elixir
+# ExUnit.configure(exclude: :pending, trace: true)
+```
+
+## Useful `mix test` options
+
+* `test/<FILE>.exs:LINENUM` - runs only a single test, the test from `<FILE>.exs` whose definition is on line `LINENUM`
+* `--failed` - runs only tests that failed the last time they ran
+* `--max-failures` - the suite stops evaluating tests when this number of test failures
+is reached
+* `--seed 0` - disables randomization so the tests in a single file will always be ran
+in the same order they were defined in
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit lib/pop_count.ex` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Elixir track's documentation](https://exercism.org/docs/tracks/elixir)
+- The [Elixir track's programming category on the forum](https://forum.exercism.org/c/programming/elixir)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+If you're stuck on something, it may help to look at some of the [available resources](https://exercism.org/docs/tracks/elixir/resources) out there where answers might be found.

elixir/pop-count/README.md

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+# Eliud's Eggs
+
+Welcome to Eliud's Eggs on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Introduction
+
+Your friend Eliud inherited a farm from her grandma Tigist.
+Her granny was an inventor and had a tendency to build things in an overly complicated manner.
+The chicken coop has a digital display showing an encoded number representing the positions of all eggs that could be picked up.
+
+Eliud is asking you to write a program that shows the actual number of eggs in the coop.
+
+The position information encoding is calculated as follows:
+
+1. Scan the potential egg-laying spots and mark down a `1` for an existing egg or a `0` for an empty spot.
+2. Convert the number from binary to decimal.
+3. Show the result on the display.
+
+Example 1:
+
+```text
+Chicken Coop:
+ _ _ _ _ _ _ _
+|E| |E|E| | |E|
+
+Resulting Binary:
+ 1 0 1 1 0 0 1
+
+Decimal number on the display:
+89
+
+Actual eggs in the coop:
+4
+```
+
+Example 2:
+
+```text
+Chicken Coop:
+ _ _ _ _ _ _ _ _
+| | | |E| | | | |
+
+Resulting Binary:
+ 0 0 0 1 0 0 0 0
+
+Decimal number on the display:
+16
+
+Actual eggs in the coop:
+1
+```
+
+## Instructions
+
+Your task is to count the number of 1 bits in the binary representation of a number.
+
+## Restrictions
+
+Keep your hands off that bit-count functionality provided by your standard library!
+Solve this one yourself using other basic tools instead.
+
+## Source
+
+### Created by
+
+- @kahgoh
+
+### Based on
+
+Christian Willner, Eric Willigers - https://forum.exercism.org/t/new-exercise-suggestion-pop-count/7632/5

elixir/pop-count/lib/pop_count.ex

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+defmodule PopCount do
+  @doc """
+  Given the number, count the number of eggs.
+  """
+  @spec egg_count(number :: integer()) :: non_neg_integer()
+  def egg_count(number) do
+    for(<<bit::1 <- :binary.encode_unsigned(number)>>, do: bit) |> Enum.sum
+  end
+
+  # @spec egg_count(number :: integer()) :: non_neg_integer()
+  # def egg_count(number) do
+  #   result =
+  #     number
+  #     |> Integer.digits(2)
+  #     |> Enum.reduce(%{binary: "", count: 0, coop: "|", length: 0}, &egg_counter/2)
+
+  #   """
+  #   Chicken Coop:
+  #   #{String.duplicate(" _", result.length)}
+  #   #{result.coop}
+
+  #   Resulting Binary:
+  #   #{result.binary}
+
+  #   Decimal number on the display:
+  #   #{number}
+
+  #   Actual eggs in the coop:
+  #   #{result.count}
+  #   """
+  #   |> IO.puts()
+
+
+  #   result.count
+  # end
+
+  # defp egg_counter(element, %{binary: binary, count: count, coop: coop, length: length} = _acc) do
+  #   char =
+  #     case element do
+  #       0 -> " "
+  #       1 -> "E"
+  #     end
+
+  #   %{
+  #     coop: coop <> char <> "|",
+  #     count: count + element,
+  #     length: length + 1,
+  #     binary: binary <> "#{element}"
+  #   }
+  # end
+end

elixir/pop-count/mix.exs

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+defmodule PopCount.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :pop_count,
+      version: "0.1.0",
+      # elixir: "~> 1.8",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

elixir/pop-count/test/pop_count_test.exs

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+defmodule PopCountTest do
+  use ExUnit.Case
+
+  describe "egg count" do
+    test "0 eggs" do
+      assert PopCount.egg_count(0) == 0
+    end
+
+    # @tag :pending
+    test "1 egg" do
+      assert PopCount.egg_count(16) == 1
+    end
+
+    # @tag :pending
+    test "4 eggs" do
+      assert PopCount.egg_count(89) == 4
+    end
+
+    # @tag :pending
+    test "13 eggs" do
+      assert PopCount.egg_count(2_000_000_000) == 13
+    end
+
+    # @tag :pending
+    test "100 eggs" do
+      assert PopCount.egg_count(1_267_650_600_228_229_401_496_703_205_375) == 100
+    end
+  end
+end

elixir/pop-count/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true)