Initial commit

elixir/secrets/.exercism/config.json

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+{
+  "authors": [
+    "neenjaw"
+  ],
+  "files": {
+    "solution": [
+      "lib/secrets.ex"
+    ],
+    "test": [
+      "test/secrets_test.exs"
+    ],
+    "exemplar": [
+      ".meta/exemplar.ex"
+    ]
+  },
+  "language_versions": ">=1.10",
+  "blurb": "Learn about bit manipulation and anonymous functions by writing the software for an encryption device."
+}

elixir/secrets/.exercism/metadata.json

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+{"track":"elixir","exercise":"secrets","id":"baa7ad210ba049e6be7ec6f9c548a06a","url":"https://exercism.org/tracks/elixir/exercises/secrets","handle":"negrienko","is_requester":true,"auto_approve":false}

elixir/secrets/.formatter.exs

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

elixir/secrets/.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").
+anonymous_functions-*.tar
+

elixir/secrets/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/secrets.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/secrets/HINTS.md

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+# Hints
+
+## General
+
+- Make use of [anonymous functions][anon-fns].
+- Use a [closure][closure] to reference the variable from the outer scope.
+
+## 1. Create an adder
+
+- Return an anonymous function which adds the argument from the anonymous function to the argument passed in to `Secret.secret_add/1`.
+
+## 2. Create a subtractor
+
+- Return an anonymous function which subtracts the argument passed in to `Secret.secret_subtract/1` from the argument from the anonymous function.
+
+## 3. Create a multiplier
+
+- Return an anonymous function which multiplies the argument from the anonymous function to the argument passed in to `Secret.secret_multiply/1`.
+
+## 4. Create a divider
+
+- Return an anonymous function which divides the argument from the anonymous function by the argument passed in to `Secret.secret_divide/1`.
+- Make use of [integer division][div].
+
+## 5. Create an "and"-er
+
+- Return an anonymous function which performs a [bitwise _and_][bitwise-wiki] operation using the argument passed in to the anonymous function and the argument passed in to `Secret.secret_and/1`
+- Functions in the [Bitwise module][bitwise-hexdocs] may be of use.
+- If you are running Elixir version 1.9 or lower, you will need to call `require Bitwise` at the beginning of the module definition to be able to use the _Bitwise_ module.
+
+## 6. Create an "xor"-er
+
+- Return an anonymous function which performs a [bitwise _xor_][bitwise-wiki] operation using the argument passed in to the anonymous function and the argument passed in to `Secret.secret_xor/1`
+- Functions in the [Bitwise module][bitwise-hexdocs] may be of use.
+- If you are running Elixir version 1.9 or lower, you will need to call `require Bitwise` at the beginning of the module definition to be able to use the _Bitwise_ module.
+
+## 7. Create a function combiner
+
+- Return an anonymous function which [composes the functions][fn-composition] passed in to `Secret.secret_combine/2`.
+- Use a `.` before `()` when calling an anonymous function.
+
+[anon-fns]: https://elixir-lang.org/getting-started/basic-types.html#anonymous-functions
+[bitwise-hexdocs]: https://hexdocs.pm/elixir/Bitwise.html
+[bitwise-wiki]: https://en.wikipedia.org/wiki/Bitwise_operation
+[closure]: https://en.wikipedia.org/wiki/Closure_(computer_programming)
+[div]: https://hexdocs.pm/elixir/Kernel.html#div/2
+[fn-composition]: https://en.wikipedia.org/wiki/Function_composition_(computer_science)

elixir/secrets/README.md

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+# Secrets
+
+Welcome to Secrets on Exercism's Elixir Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+If you get stuck on the exercise, check out `HINTS.md`, but try and solve it without using those first :)
+
+## Introduction
+
+## Anonymous Functions
+
+Functions are treated as first class citizens in Elixir. This means that:
+
+- Named and anonymous functions can be assigned to variables.
+- Named and anonymous functions can be passed around like data as arguments and return values.
+- Anonymous functions can be created dynamically.
+
+Anonymous functions, in contrast to named functions, don't have a static reference available to them, they are only available if they are assigned to a variable or immediately invoked.
+
+We might use anonymous functions to:
+
+- Hide data using lexical scope (also known as a closure).
+- Dynamically create functions at run-time.
+
+Anonymous functions start with the reserved word `fn`, the arguments are separated from the body of the function with the `->` token, and they are finished with an `end`. As with named functions, the last expression in the function is _implicitly returned_ to the calling function.
+
+To invoke a function reference, you must use a `.` between the reference variable and the list of arguments:
+
+```elixir
+function_variable = fn param ->
+  param + 1
+end
+
+function_variable.(1)
+# => 2
+```
+
+You can even use short hand capture notation to make this more concise:
+
+```elixir
+variable = &(&1 + 1)
+
+variable.(1)
+# => 2
+```
+
+## Bit Manipulation
+
+Elixir supports many functions for working with bits found in the _Bitwise module_.
+
+- `band/2`: bitwise AND
+- `bsl/2`: bitwise SHIFT LEFT
+- `bsr/2`: bitwise SHIFT RIGHT
+- `bxor/2`: bitwise XOR
+- `bor/2`: bitwise OR
+- `bnot/1`: bitwise NOT
+
+Here is an example how to use a bitwise function:
+
+```elixir
+Bitwise.bsl(1, 3)
+# => 8
+```
+
+All bitwise functions only work on integers.
+
+If you are running Elixir version 1.9 or lower, you will need to call `require Bitwise` at the beginning of the module definition to be able to use the _Bitwise_ module.
+
+## Instructions
+
+In this exercise, you've been tasked with writing the software for an encryption device that works by performing transformations on data. You need a way to flexibly create complicated functions by combining simpler functions together.
+
+For each task, return an anonymous function that can be invoked from the calling scope.
+
+All functions should expect integer arguments. Integers are also suitable for performing bitwise operations in Elixir.
+
+## 1. Create an adder
+
+Implement `Secrets.secret_add/1`. It should return a function which takes one argument and adds to it the argument passed in to `secret_add`.
+
+```elixir
+adder = Secrets.secret_add(2)
+adder.(2)
+# => 4
+```
+
+## 2. Create a subtractor
+
+Implement `Secrets.secret_subtract/1`. It should return a function which takes one argument and subtracts the secret passed in to `secret_subtract` from that argument.
+
+```elixir
+subtractor = Secrets.secret_subtract(2)
+subtractor.(3)
+# => 1
+```
+
+## 3. Create a multiplier
+
+Implement `Secrets.secret_multiply/1`. It should return a function which takes one argument and multiplies it by the secret passed in to `secret_multiply`.
+
+```elixir
+multiplier = Secrets.secret_multiply(7)
+multiplier.(3)
+# => 21
+```
+
+## 4. Create a divider
+
+Implement `Secrets.secret_divide/1`. It should return a function which takes one argument and divides it by the secret passed in to `secret_divide`.
+
+```elixir
+divider = Secrets.secret_divide(3)
+divider.(32)
+# => 10
+```
+
+Make use of integer division so the output is compatible with the other functions' expected input.
+
+## 5. Create an "and"-er
+
+Implement `Secrets.secret_and/1`. It should return a function which takes one argument and performs a bitwise _and_ operation on it and the secret passed in to `secret_and`.
+
+```elixir
+ander = Secrets.secret_and(1)
+ander.(2)
+# => 0
+```
+
+## 6. Create an "xor"-er
+
+Implement `Secrets.secret_xor/1`. It should return a function which takes one argument and performs a bitwise _xor_ operation on it and the secret passed in to `secret_xor`.
+
+```elixir
+xorer = Secrets.secret_xor(1)
+xorer.(3)
+# => 2
+```
+
+## 7. Create a function combiner
+
+Implement `Secrets.secret_combine/2`. It should return a function which takes one argument and applies to it the two functions passed in to `secret_combine` in order.
+
+```elixir
+multiply = Secrets.secret_multiply(7)
+divide = Secrets.secret_divide(3)
+combined = Secrets.secret_combine(multiply, divide)
+
+combined.(6)
+# => 14
+```
+
+## Source
+
+### Created by
+
+- @neenjaw

elixir/secrets/lib/secrets.ex

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+defmodule Secrets do
+  def secret_add(secret) do
+    &(&1 + secret)
+  end
+
+  def secret_subtract(secret) do
+    &(&1 - secret)
+  end
+
+  def secret_multiply(secret) do
+    &(&1 * secret)
+  end
+
+  def secret_divide(secret) do
+    &(div(&1, secret))
+  end
+
+  def secret_and(secret) do
+    &(Bitwise.band(secret, &1))
+  end
+
+  def secret_xor(secret) do
+    &(Bitwise.bxor(secret, &1))
+  end
+
+  def secret_combine(secret_function1, secret_function2) do
+    &(secret_function2.(secret_function1.(&1)))
+  end
+end

elixir/secrets/mix.exs

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+defmodule Secrets.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :secrets,
+      version: "0.1.0",
+      # elixir: "~> 1.10",
+      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/secrets/test/secrets_test.exs

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+defmodule SecretsTest do
+  use ExUnit.Case
+
+  describe "secret_add" do
+    @tag task_id: 1
+    test "add 3" do
+      add = Secrets.secret_add(3)
+      assert add.(3) === 6
+    end
+
+    @tag task_id: 1
+    test "add 6" do
+      add = Secrets.secret_add(6)
+      assert add.(9) === 15
+    end
+  end
+
+  describe "secret_subtract" do
+    @tag task_id: 2
+    test "subtract 3" do
+      subtract = Secrets.secret_subtract(3)
+      assert subtract.(6) === 3
+    end
+
+    @tag task_id: 2
+    test "subtract 6" do
+      subtract = Secrets.secret_subtract(6)
+      assert subtract.(3) === -3
+    end
+  end
+
+  describe "secret_multiply" do
+    @tag task_id: 3
+    test "multiply by 3" do
+      multiply = Secrets.secret_multiply(3)
+      assert multiply.(6) === 18
+    end
+
+    @tag task_id: 3
+    test "multiply by 6" do
+      multiply = Secrets.secret_multiply(6)
+      assert multiply.(7) === 42
+    end
+  end
+
+  describe "secret_divide" do
+    @tag task_id: 4
+    test "divide by 3" do
+      divide = Secrets.secret_divide(3)
+      assert divide.(6) === 2
+    end
+
+    @tag task_id: 4
+    test "divide by 6" do
+      divide = Secrets.secret_divide(6)
+      assert divide.(7) === 1
+    end
+  end
+
+  describe "secret_and" do
+    @tag task_id: 5
+    test "2 and 1" do
+      ander = Secrets.secret_and(1)
+      assert ander.(2) === 0
+    end
+
+    @tag task_id: 5
+    test "7 and 7" do
+      ander = Secrets.secret_and(7)
+      assert ander.(7) === 7
+    end
+  end
+
+  describe "secret_xor" do
+    @tag task_id: 6
+    test "2 xor 1" do
+      xorer = Secrets.secret_xor(1)
+      assert xorer.(2) === 3
+    end
+
+    @tag task_id: 6
+    test "7 xor 7" do
+      xorer = Secrets.secret_xor(7)
+      assert xorer.(7) === 0
+    end
+  end
+
+  describe "secret_combine" do
+    @tag task_id: 7
+    test "5 add 10 then subtract 5" do
+      f = Secrets.secret_add(10)
+      g = Secrets.secret_subtract(5)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(5) === 10
+    end
+
+    @tag task_id: 7
+    test "100 multiply by 2 then subtract 20" do
+      f = Secrets.secret_multiply(2)
+      g = Secrets.secret_subtract(20)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(100) === 180
+    end
+
+    @tag task_id: 7
+    test "100 divide by 10 then add 10" do
+      f = Secrets.secret_divide(10)
+      g = Secrets.secret_add(10)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(100) === 20
+    end
+
+    @tag task_id: 7
+    test "32 divide by 3 then add 5" do
+      f = Secrets.secret_divide(3)
+      g = Secrets.secret_add(5)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(32) === 15
+    end
+
+    @tag task_id: 7
+    test "7 and 3 then and 5" do
+      f = Secrets.secret_and(3)
+      g = Secrets.secret_and(5)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(7) === 1
+    end
+
+    @tag task_id: 7
+    test "7 and 7 then and 7" do
+      f = Secrets.secret_and(7)
+      g = Secrets.secret_and(7)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(7) === 7
+    end
+
+    @tag task_id: 7
+    test "4 xor 1 then xor 2" do
+      f = Secrets.secret_xor(1)
+      g = Secrets.secret_xor(2)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(4) === 7
+    end
+
+    @tag task_id: 7
+    test "7 xor 7 then xor 7" do
+      f = Secrets.secret_xor(7)
+      g = Secrets.secret_xor(7)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(7) === 7
+    end
+
+    @tag task_id: 7
+    test "4 add 3 then xor 7" do
+      f = Secrets.secret_add(3)
+      g = Secrets.secret_xor(7)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(4) === 0
+    end
+
+    @tag task_id: 7
+    test "81 divide by 9 then and 7" do
+      f = Secrets.secret_divide(9)
+      g = Secrets.secret_and(7)
+      h = Secrets.secret_combine(f, g)
+
+      assert h.(81) === 1
+    end
+  end
+end

elixir/secrets/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true, seed: 0)