Add Space Age

Author: ricardomaps

config.json

@@ -418,6 +418,14 @@
         "prerequisites": [],
         "difficulty": 3
       },
+      {
+        "slug": "space-age",
+        "name": "Space Age",
+        "uuid": "d7f34974-403b-43c4-8882-48fa710f0983",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "square-root",
         "name": "Square Root",

exercises/practice/space-age/.docs/instructions.md

@@ -0,0 +1,28 @@
+# 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
+~~~~

exercises/practice/space-age/.docs/introduction.md

@@ -0,0 +1,20 @@
+# 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
+~~~~

exercises/practice/space-age/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ricardomaps"
+  ],
+  "files": {
+    "solution": [
+      "space-age.nix"
+    ],
+    "test": [
+      "space-age-test.nix"
+    ],
+    "example": [
+      ".meta/example.nix"
+    ]
+  },
+  "blurb": "Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.",
+  "source": "Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial.",
+  "source_url": "https://pine.fm/LearnToProgram/chap_01.html"
+}

exercises/practice/space-age/.meta/example.nix

@@ -0,0 +1,20 @@
+let
+  orbitalPeriods = {
+    Mercury = 0.2408467;
+    Venus = 0.61519726;
+    Earth = 1.0;
+    Mars = 1.8808158;
+    Jupiter = 11.862615;
+    Saturn = 29.447498;
+    Uranus = 84.016846;
+    Neptune = 164.79132;
+  };
+in
+{
+  age =
+    planet: seconds:
+    if (orbitalPeriods ? ${planet}) then
+      seconds / (31557600 * orbitalPeriods.${planet})
+    else
+      throw "not a planet";
+}

exercises/practice/space-age/.meta/tests.toml

@@ -0,0 +1,37 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[84f609af-5a91-4d68-90a3-9e32d8a5cd34]
+description = "age on Earth"
+
+[ca20c4e9-6054-458c-9312-79679ffab40b]
+description = "age on Mercury"
+
+[502c6529-fd1b-41d3-8fab-65e03082b024]
+description = "age on Venus"
+
+[9ceadf5e-a0d5-4388-9d40-2c459227ceb8]
+description = "age on Mars"
+
+[42927dc3-fe5e-4f76-a5b5-f737fc19bcde]
+description = "age on Jupiter"
+
+[8469b332-7837-4ada-b27c-00ee043ebcad]
+description = "age on Saturn"
+
+[999354c1-76f8-4bb5-a672-f317b6436743]
+description = "age on Uranus"
+
+[80096d30-a0d4-4449-903e-a381178355d8]
+description = "age on Neptune"
+
+[57b96e2a-1178-40b7-b34d-f3c9c34e4bf4]
+description = "invalid planet causes error"

exercises/practice/space-age/space-age-test.nix

@@ -0,0 +1,44 @@
+let
+  inherit (import ./space-age.nix) age;
+  abs = val: if val < 0 then -val else val;
+  inDelta = actual: expected: abs (actual - expected) < 0.005;
+in
+{
+  "test age on Earth" = {
+    expr = inDelta (age "Earth" 1000000000) 31.69;
+    expected = true;
+  };
+  "test age on Mercury" = {
+    expr = inDelta (age "Mercury" 2134835688) 280.88;
+    expected = true;
+  };
+  "test age on Venus" = {
+    expr = inDelta (age "Venus" 189839836) 9.78;
+    expected = true;
+  };
+  "test age on Mars" = {
+    expr = inDelta (age "Mars" 2129871239) 35.88;
+    expected = true;
+  };
+  "test age on Jupiter" = {
+    expr = inDelta (age "Jupiter" 901876382) 2.41;
+    expected = true;
+  };
+  "test age on Saturn" = {
+    expr = inDelta (age "Saturn" 2000000000) 2.15;
+    expected = true;
+  };
+  "test age on Uranus" = {
+    expr = inDelta (age "Uranus" 1210123456) 0.46;
+    expected = true;
+  };
+  "test age on Neptune" = {
+    expr = inDelta (age "Neptune" 1821023456) 0.35;
+    expected = true;
+  };
+  "test invalid planet causes error" = {
+    expr = age "Sun" 680804807;
+    expectedError.type = "ThrownError";
+    expectedError.msg = "not a planet";
+  };
+}

exercises/practice/space-age/space-age.nix

@@ -0,0 +1,3 @@
+{
+  age = planet: seconds: throw "You need to implement this function.";
+}