space-age

rust/space-age/README.md

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+# Space Age
+
+Welcome to Space Age on Exercism's Rust Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Introduction
+
+The year is 2525 and you've just embarked on a journey to visit all planets in the Solar System (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune).
+The first stop is Mercury, where customs require you to fill out a form (bureaucracy is apparently _not_ Earth-specific).
+As you hand over the form to the customs officer, they scrutinize it and frown.
+"Do you _really_ expect me to believe you're just 50 years old?
+You must be closer to 200 years old!"
+
+Amused, you wait for the customs officer to start laughing, but they appear to be dead serious.
+You realize that you've entered your age in _Earth years_, but the officer expected it in _Mercury years_!
+As Mercury's orbital period around the sun is significantly shorter than Earth, you're actually a lot older in Mercury years.
+After some quick calculations, you're able to provide your age in Mercury Years.
+The customs officer smiles, satisfied, and waves you through.
+You make a mental note to pre-calculate your planet-specific age _before_ future customs checks, to avoid such mix-ups.
+
+~~~~exercism/note
+If you're wondering why Pluto didn't make the cut, go watch [this YouTube video][pluto-video].
+
+[pluto-video]: https://www.youtube.com/watch?v=Z_2gbGXzFbs
+~~~~
+
+## Instructions
+
+Given an age in seconds, calculate how old someone would be on a planet in our Solar System.
+
+One Earth year equals 365.25 Earth days, or 31,557,600 seconds.
+If you were told someone was 1,000,000,000 seconds old, their age would be 31.69 Earth-years.
+
+For the other planets, you have to account for their orbital period in Earth Years:
+
+| Planet  | Orbital period in Earth Years |
+| ------- | ----------------------------- |
+| Mercury | 0.2408467                     |
+| Venus   | 0.61519726                    |
+| Earth   | 1.0                           |
+| Mars    | 1.8808158                     |
+| Jupiter | 11.862615                     |
+| Saturn  | 29.447498                     |
+| Uranus  | 84.016846                     |
+| Neptune | 164.79132                     |
+
+~~~~exercism/note
+The actual length of one complete orbit of the Earth around the sun is closer to 365.256 days (1 sidereal year).
+The Gregorian calendar has, on average, 365.2425 days.
+While not entirely accurate, 365.25 is the value used in this exercise.
+See [Year on Wikipedia][year] for more ways to measure a year.
+
+[year]: https://en.wikipedia.org/wiki/Year#Summary
+~~~~
+
+## Topics
+
+Some Rust topics you may want to read about while solving this problem:
+
+- Traits, both the From trait and [implementing your own traits](https://doc.rust-lang.org/book/ch10-02-traits.html)
+- [Default method implementations](https://doc.rust-lang.org/book/ch10-02-traits.html#default-implementations) for traits
+- Macros, the use of a macro could reduce boilerplate and increase readability
+  for this exercise. For instance,
+  [a macro can implement a trait for multiple types at once](https://stackoverflow.com/questions/39150216/implementing-a-trait-for-multiple-types-at-once),
+  though it is fine to implement `years_during` in the Planet trait itself. A macro could
+  define both the structs and their implementations. Info to get started with macros can
+  be found at:
+
+  - [The Macros chapter in The Rust Programming Language](https://doc.rust-lang.org/stable/book/ch19-06-macros.html)
+  - [an older version of the Macros chapter with helpful detail](https://doc.rust-lang.org/1.30.0/book/first-edition/macros.html)
+  - [Rust By Example](https://doc.rust-lang.org/stable/rust-by-example/macros.html)
+
+## Source
+
+### Created by
+
+- @IanWhitney
+
+### Contributed to by
+
+- @ashleygwilliams
+- @bobahop
+- @coriolinus
+- @cwhakes
+- @durka
+- @eddyp
+- @efx
+- @ErikSchierboom
+- @IanWhitney
+- @joshgoebel
+- @lutostag
+- @nfiles
+- @ocstl
+- @petertseng
+- @rofrol
+- @stringparser
+- @xakon
+- @ZapAnton
+
+### Based on
+
+Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. - https://pine.fm/LearnToProgram/?Chapter=01