From d1b894006cfe22853ac425ee81e45884992d8e20 Mon Sep 17 00:00:00 2001 From: Danylo Negrienko Date: Thu, 7 Mar 2024 01:40:53 -0500 Subject: [PATCH] rpn_calculator --- elixir/rpn-calculator/.exercism/config.json | 23 ++++ elixir/rpn-calculator/.exercism/metadata.json | 1 + elixir/rpn-calculator/.formatter.exs | 4 + elixir/rpn-calculator/.gitignore | 24 ++++ elixir/rpn-calculator/HELP.md | 75 +++++++++++ elixir/rpn-calculator/HINTS.md | 23 ++++ elixir/rpn-calculator/README.md | 121 ++++++++++++++++++ elixir/rpn-calculator/lib/rpn_calculator.ex | 21 +++ elixir/rpn-calculator/mix.exs | 28 ++++ .../test/rpn_calculator_test.exs | 55 ++++++++ elixir/rpn-calculator/test/test_helper.exs | 2 + 11 files changed, 377 insertions(+) create mode 100644 elixir/rpn-calculator/.exercism/config.json create mode 100644 elixir/rpn-calculator/.exercism/metadata.json create mode 100644 elixir/rpn-calculator/.formatter.exs create mode 100644 elixir/rpn-calculator/.gitignore create mode 100644 elixir/rpn-calculator/HELP.md create mode 100644 elixir/rpn-calculator/HINTS.md create mode 100644 elixir/rpn-calculator/README.md create mode 100644 elixir/rpn-calculator/lib/rpn_calculator.ex create mode 100644 elixir/rpn-calculator/mix.exs create mode 100644 elixir/rpn-calculator/test/rpn_calculator_test.exs create mode 100644 elixir/rpn-calculator/test/test_helper.exs diff --git a/elixir/rpn-calculator/.exercism/config.json b/elixir/rpn-calculator/.exercism/config.json new file mode 100644 index 0000000..3767236 --- /dev/null +++ b/elixir/rpn-calculator/.exercism/config.json @@ -0,0 +1,23 @@ +{ + "authors": [ + "neenjaw" + ], + "contributors": [ + "angelikatyborska", + "cjmaxik" + ], + "files": { + "solution": [ + "lib/rpn_calculator.ex" + ], + "test": [ + "test/rpn_calculator_test.exs" + ], + "exemplar": [ + ".meta/exemplar.ex" + ] + }, + "language_versions": ">=1.10", + "icon": "instruments-of-texas", + "blurb": "Learn about errors and rescuing them by working on an experimental Reverse Polish Notation calculator." +} diff --git a/elixir/rpn-calculator/.exercism/metadata.json b/elixir/rpn-calculator/.exercism/metadata.json new file mode 100644 index 0000000..bf43c32 --- /dev/null +++ b/elixir/rpn-calculator/.exercism/metadata.json @@ -0,0 +1 @@ +{"track":"elixir","exercise":"rpn-calculator","id":"ea46ce98f99e40f18d385997dfdae1de","url":"https://exercism.org/tracks/elixir/exercises/rpn-calculator","handle":"negrienko","is_requester":true,"auto_approve":false} \ No newline at end of file diff --git a/elixir/rpn-calculator/.formatter.exs b/elixir/rpn-calculator/.formatter.exs new file mode 100644 index 0000000..d2cda26 --- /dev/null +++ b/elixir/rpn-calculator/.formatter.exs @@ -0,0 +1,4 @@ +# Used by "mix format" +[ + inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"] +] diff --git a/elixir/rpn-calculator/.gitignore b/elixir/rpn-calculator/.gitignore new file mode 100644 index 0000000..d343c0d --- /dev/null +++ b/elixir/rpn-calculator/.gitignore @@ -0,0 +1,24 @@ +# 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"). +errors-*.tar + diff --git a/elixir/rpn-calculator/HELP.md b/elixir/rpn-calculator/HELP.md new file mode 100644 index 0000000..257795c --- /dev/null +++ b/elixir/rpn-calculator/HELP.md @@ -0,0 +1,75 @@ +# 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/.exs:LINENUM` - runs only a single test, the test from `.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/rpn_calculator.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. \ No newline at end of file diff --git a/elixir/rpn-calculator/HINTS.md b/elixir/rpn-calculator/HINTS.md new file mode 100644 index 0000000..c94e43c --- /dev/null +++ b/elixir/rpn-calculator/HINTS.md @@ -0,0 +1,23 @@ +# Hints + +## General + +- Read about [errors][errors] in the Getting Started guide. +- Read about [`try`][docs-try] in the documentation. + +## 1. Warn the team + +- Allow the operation function to raise its error. +- To invoke a function in a variable, use the `.` operator. + +## 2. Wrap the error + +- Make use of try .. rescue to return the intended result. + +## 3. Pass on the message + +- Make use of try .. rescue to return the intended result. +- The rescue block allows you to pattern match on the error's Module name and also bind the error to a variable. + +[errors]: https://hexdocs.pm/elixir/try-catch-and-rescue.html#errors +[docs-try]: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#try/1 \ No newline at end of file diff --git a/elixir/rpn-calculator/README.md b/elixir/rpn-calculator/README.md new file mode 100644 index 0000000..4d24160 --- /dev/null +++ b/elixir/rpn-calculator/README.md @@ -0,0 +1,121 @@ +# RPN Calculator + +Welcome to RPN Calculator 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 + +## Errors + +Errors happen. In Elixir, while people often say to "let it crash", there are times when we need to rescue the function call to a known good state to fulfill a software contract. In some languages, errors are used as a method of control flow, but in Elixir, this pattern is discouraged. We can often recognize functions that may raise an error just by their name: functions that raise errors are to have `!` at the end of their name. This is in comparison with functions that return `{:ok, value}` or `:error`. Look at these library examples: + +```elixir +Map.fetch(%{a: 1}, :b) +# => :error +Map.fetch!(%{a: 1}, :b) +# => raises KeyError +``` + +## Try/Rescue + +Elixir provides a construct for rescuing from errors using `try .. rescue` + +[]: # (elixir-formatter-disable-next-block) + +```elixir +try do #1 + raise RuntimeError, "error" #2 +rescue + e in RuntimeError -> :error #3 +end +``` + +Let's examine this construct: + +- **Line 1**, the block is declared with `try`. +- **Line 2**, the function call which may error is placed here, in this case we are calling `raise/2`. +- **Line 3**, in the `rescue` section, we pattern match on the _Module_ name of the error raised + - on the left side of `->`: + - `e` is matched to the error struct. + - `in` is a keyword. + - `RuntimeError` is the error that we want to rescue. + - If we wanted to rescue from all errors, we could use `_` instead of the module name or omit the `in` keyword entirely. + - on the right side: + - the instructions to be executed if the error matches. + +### Error structs + +Errors (sometimes also called "exceptions") that you rescue this way are structs. +Rescuing errors in Elixir is done very rarely. +Usually the rescued error is logged or sent to an external monitoring service, and then reraised. +This means we usually don't care about the internal structure of the specific error struct. + +In the [Exceptions concept][exercism-exceptions] you will learn more about error structs, including how to define your own custom error. + +[exercism-exceptions]: https://exercism.org/tracks/elixir/concepts/exceptions + +## Instructions + +While working at _Instruments of Texas_, you are tasked to work on an experimental Reverse Polish Notation [RPN] calculator written in Elixir. Your team is having a problem with some operations raising errors and crashing the process. You have been tasked to write a function which wraps the operation function so that the errors can be handled more elegantly with idiomatic Elixir code. + +## 1. Warn the team + +Implement the function `calculate!/2` to call the operation function with the stack as the only argument. The operation function is defined elsewhere, but you know that it can either complete successfully or raise an error. + +```elixir +stack = [] +operation = fn _ -> :ok end +RPNCalculator.calculate!(stack, operation) +# => :ok + +stack = [] +operation = fn _ -> raise ArgumentError, "An error occurred" end +RPNCalculator.calculate!(stack, operation) +# => ** (ArgumentError) An error occurred +``` + +> Function names that end in `!` are a warning to programmers that this function may raise an error + +## 2. Wrap the error + +When doing more research you notice that many functions use atoms and tuples to indicate their success/failure. Implement `calculate/2` using this strategy. + +```elixir +stack = [] +operation = fn _ -> "operation completed" end +RPNCalculator.calculate(stack, operation) +# => {:ok, "operation completed"} + +stack = [] +operation = fn _ -> raise ArgumentError, "An error occurred" end +RPNCalculator.calculate(stack, operation) +# => :error +``` + +## 3. Pass on the message + +Some of the errors contain important information that your coworkers need to have to ensure the correct operation of the system. Implement `calculate_verbose/2` to pass on the error message. The error is a struct that has a `:message` field. + +```elixir +stack = [] +operation = fn _ -> "operation completed" end +RPNCalculator.calculate_verbose(stack, operation) +# => {:ok, "operation completed"} + +stack = [] +operation = fn _ -> raise ArgumentError, "An error occurred" end +RPNCalculator.calculate_verbose(stack, operation) +# => {:error, "An error occurred"} +``` + +## Source + +### Created by + +- @neenjaw + +### Contributed to by + +- @angelikatyborska +- @cjmaxik \ No newline at end of file diff --git a/elixir/rpn-calculator/lib/rpn_calculator.ex b/elixir/rpn-calculator/lib/rpn_calculator.ex new file mode 100644 index 0000000..bfbb10d --- /dev/null +++ b/elixir/rpn-calculator/lib/rpn_calculator.ex @@ -0,0 +1,21 @@ +defmodule RPNCalculator do + def calculate!(stack, operation) do + operation.(stack) + end + + def calculate(stack, operation) do + try do + {:ok, operation.(stack)} + rescue + _e -> :error + end + end + + def calculate_verbose(stack, operation) do + try do + {:ok, operation.(stack)} + rescue + e -> {:error, e.message} + end + end +end diff --git a/elixir/rpn-calculator/mix.exs b/elixir/rpn-calculator/mix.exs new file mode 100644 index 0000000..de2dbe1 --- /dev/null +++ b/elixir/rpn-calculator/mix.exs @@ -0,0 +1,28 @@ +defmodule RPNCalculator.MixProject do + use Mix.Project + + def project do + [ + app: :rpn_calculator, + 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 diff --git a/elixir/rpn-calculator/test/rpn_calculator_test.exs b/elixir/rpn-calculator/test/rpn_calculator_test.exs new file mode 100644 index 0000000..a2aa18b --- /dev/null +++ b/elixir/rpn-calculator/test/rpn_calculator_test.exs @@ -0,0 +1,55 @@ +defmodule RPNCalculatorTest do + use ExUnit.Case + + @tag task_id: 1 + test "calculate! returns what the operation does: :ok atom" do + assert RPNCalculator.calculate!([], fn _ -> :ok end) == :ok + end + + @tag task_id: 1 + test "calculate! returns what the operation does: an ok string" do + assert RPNCalculator.calculate!([], fn _ -> "ok" end) == "ok" + end + + @tag task_id: 1 + test "let it crash" do + assert_raise(RuntimeError, fn -> + RPNCalculator.calculate!([], fn _ -> raise "test error" end) + end) + end + + @tag task_id: 2 + test "calculate returns the result of the operation (a string) wrapped in an :ok tuple" do + assert RPNCalculator.calculate([], fn _ -> "operation completed" end) == + {:ok, "operation completed"} + end + + @tag task_id: 2 + test "calculate returns the result of the operation (an atom) wrapped in an :ok tuple" do + assert RPNCalculator.calculate([], fn _ -> :success end) == + {:ok, :success} + end + + @tag task_id: 2 + test "rescue the crash, no message" do + assert RPNCalculator.calculate([], fn _ -> raise "test error" end) == :error + end + + @tag task_id: 3 + test "calculate_verbose returns the result of the operation (a string) wrapped in an :ok tuple" do + assert RPNCalculator.calculate_verbose([], fn _ -> "operation completed" end) == + {:ok, "operation completed"} + end + + @tag task_id: 3 + test "calculate_verbose returns the result of the operation (an atom) wrapped in an :ok tuple" do + assert RPNCalculator.calculate_verbose([], fn _ -> :success end) == + {:ok, :success} + end + + @tag task_id: 3 + test "rescue the crash, get error tuple with message" do + assert RPNCalculator.calculate_verbose([], fn _ -> raise ArgumentError, "test error" end) == + {:error, "test error"} + end +end diff --git a/elixir/rpn-calculator/test/test_helper.exs b/elixir/rpn-calculator/test/test_helper.exs new file mode 100644 index 0000000..e8677a3 --- /dev/null +++ b/elixir/rpn-calculator/test/test_helper.exs @@ -0,0 +1,2 @@ +ExUnit.start() +ExUnit.configure(exclude: :pending, trace: true, seed: 0)