exercise: add clock (#8)

Author: ruancomelli

exercism/rust/clock/.exercism/config.json

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+{
+  "authors": [
+    "sacherjj"
+  ],
+  "contributors": [
+    "attilahorvath",
+    "coriolinus",
+    "cwhakes",
+    "danieljl",
+    "eddyp",
+    "efx",
+    "ErikSchierboom",
+    "felix91gr",
+    "kunaltyagi",
+    "lutostag",
+    "nfiles",
+    "petertseng",
+    "rofrol",
+    "shaaraddalvi",
+    "stringparser",
+    "tmccombs",
+    "xakon",
+    "ZapAnton"
+  ],
+  "files": {
+    "solution": [
+      "src/lib.rs",
+      "Cargo.toml"
+    ],
+    "test": [
+      "tests/clock.rs"
+    ],
+    "example": [
+      ".meta/example.rs"
+    ]
+  },
+  "blurb": "Implement a clock that handles times without dates.",
+  "source": "Pairing session with Erin Drummond",
+  "source_url": "https://twitter.com/ebdrummond",
+  "custom": {
+    "allowed-to-not-compile": "Stub doesn't compile because there is no to_string() implementation. This exercise is an introduction to derived and self-implemented traits, therefore adding template for a trait would reduce student learning."
+  }
+}

exercism/rust/clock/.exercism/metadata.json

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+{"track":"rust","exercise":"clock","id":"881fe91ec3d349b7bdadfa3e591006b2","url":"https://exercism.org/tracks/rust/exercises/clock","handle":"ruancomelli","is_requester":true,"auto_approve":false}

exercism/rust/clock/.gitignore

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+# Generated by Cargo
+# will have compiled files and executables
+/target/
+**/*.rs.bk
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock

exercism/rust/clock/Cargo.toml

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+[package]
+edition = "2021"
+name = "clock"
+version = "2.4.0"
+
+[dependencies]

exercism/rust/clock/HELP.md

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+# Help
+
+## Running the tests
+
+Execute the tests with:
+
+```bash
+$ cargo test
+```
+
+All but the first test have been ignored. After you get the first test to
+pass, open the tests source file which is located in the `tests` directory
+and remove the `#[ignore]` flag from the next test and get the tests to pass
+again. Each separate test is a function with `#[test]` flag above it.
+Continue, until you pass every test.
+
+If you wish to run _only ignored_ tests without editing the tests source file, use:
+
+```bash
+$ cargo test -- --ignored
+```
+
+If you are using Rust 1.51 or later, you can run _all_ tests with
+
+```bash
+$ cargo test -- --include-ignored
+```
+
+To run a specific test, for example `some_test`, you can use:
+
+```bash
+$ cargo test some_test
+```
+
+If the specific test is ignored, use:
+
+```bash
+$ cargo test some_test -- --ignored
+```
+
+To learn more about Rust tests refer to the online [test documentation][rust-tests].
+
+[rust-tests]: https://doc.rust-lang.org/book/ch11-02-running-tests.html
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit src/lib.rs Cargo.toml` 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 [Rust track's documentation](https://exercism.org/docs/tracks/rust)
+- [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.
+
+## Rust Installation
+
+Refer to the [exercism help page][help-page] for Rust installation and learning
+resources.
+
+## Submitting the solution
+
+Generally you should submit all files in which you implemented your solution (`src/lib.rs` in most cases). If you are using any external crates, please consider submitting the `Cargo.toml` file. This will make the review process faster and clearer.
+
+## Feedback, Issues, Pull Requests
+
+The GitHub [track repository][github] is the home for all of the Rust exercises. If you have feedback about an exercise, or want to help implement new exercises, head over there and create an issue. Members of the rust track team are happy to help!
+
+If you want to know more about Exercism, take a look at the [contribution guide].
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+
+[help-page]: https://exercism.org/tracks/rust/learning
+[github]: https://github.com/exercism/rust
+[contribution guide]: https://exercism.org/docs/community/contributors

exercism/rust/clock/README.md

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+# Clock
+
+Welcome to Clock on Exercism's Rust Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Implement a clock that handles times without dates.
+
+You should be able to add and subtract minutes to it.
+
+Two clocks that represent the same time should be equal to each other.
+
+You will also need to implement `.to_string()` for the `Clock` struct. We will be using this to display the Clock's state.  You can either do it via implementing it directly or using the [Display trait](https://doc.rust-lang.org/std/fmt/trait.Display.html).
+
+Did you implement `.to_string()` for the `Clock` struct?
+
+If so, try implementing the
+[Display trait](https://doc.rust-lang.org/std/fmt/trait.Display.html) for `Clock` instead.
+
+Traits allow for a common way to implement functionality for various types.
+
+For additional learning, consider how you might implement `String::from` for the `Clock` type.
+You don't have to actually implement this—it's redundant with `Display`, which is generally the
+better choice when the destination type is `String`—but it's useful to have a few type-conversion
+traits in your toolkit.
+
+## Source
+
+### Created by
+
+- @sacherjj
+
+### Contributed to by
+
+- @attilahorvath
+- @coriolinus
+- @cwhakes
+- @danieljl
+- @eddyp
+- @efx
+- @ErikSchierboom
+- @felix91gr
+- @kunaltyagi
+- @lutostag
+- @nfiles
+- @petertseng
+- @rofrol
+- @shaaraddalvi
+- @stringparser
+- @tmccombs
+- @xakon
+- @ZapAnton
+
+### Based on
+
+Pairing session with Erin Drummond - https://twitter.com/ebdrummond

exercism/rust/clock/src/lib.rs

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+use std::fmt;
+
+const MINUTES_PER_HOUR: i32 = 60;
+const MINUTES_PER_DAY: i32 = 24 * MINUTES_PER_HOUR;
+
+
+#[derive(fmt::Debug, PartialEq)]
+pub struct Clock(i32);
+
+impl Clock {
+    pub fn new(hours: i32, minutes: i32) -> Self {
+        Clock((hours * MINUTES_PER_HOUR + minutes).rem_euclid(MINUTES_PER_DAY))
+    }
+
+    pub fn add_minutes(&self, minutes: i32) -> Self {
+        Clock::new(0, self.0 + minutes)
+    }
+}
+
+impl fmt::Display for Clock {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{:02}:{:02}", self.0 / MINUTES_PER_HOUR, self.0 % MINUTES_PER_HOUR)
+    }
+}