Merge pull request #15 from tmcgilchrist/space-age

Solution for space age.

Author: kytrinyx

config.json

@@ -8,9 +8,10 @@
     "rna-transcription",
     "accumulate",
     "bob",
-    "sum-of-multiples",	
+    "sum-of-multiples",
     "strain",
     "point-mutations",
+    "space-age",
     "anagram",
     "nucleotide-count",
     "phone-number",

space-age/example.erl

@@ -0,0 +1,28 @@
+-module(space_age).
+
+-export([ageOn/2]).
+
+-type planets() :: mercury | venus | earth | mars | jupiter | saturn | uranus | neptune.
+-spec ageOn(planets(), integer()) -> float().
+ageOn(Planet, Seconds) ->
+    Seconds / secondsPerYear(Planet).
+
+secondsPerYear (mercury) ->
+    earthYear() * 0.2408467;
+secondsPerYear (venus) ->
+    earthYear() * 0.61519726;
+secondsPerYear (earth) ->
+    earthYear();
+secondsPerYear (mars) ->
+    earthYear() * 1.8808158;
+secondsPerYear (jupiter) ->
+    earthYear() * 11.862615;
+secondsPerYear (saturn) ->
+    earthYear() * 29.447498;
+secondsPerYear (uranus) ->
+    earthYear() * 84.016846;
+secondsPerYear (neptune) ->
+    earthYear() * 164.79132.
+
+earthYear() ->
+    365.25 * 24 * 60 * 60.

space-age/space_age_test.erl

@@ -0,0 +1,48 @@
+-module(space_age_test).
+
+-include_lib("eunit/include/eunit.hrl").
+
+age_in_earth_years_test() ->
+    equalFloat(space_age:ageOn(earth, 1000000000), 31.69).
+
+age_in_mercury_years_test() ->
+    Seconds = 2134835688,
+    equalFloat(space_age:ageOn(earth, Seconds), 67.65),
+    equalFloat(space_age:ageOn(mercury, Seconds), 280.88).
+
+age_in_venus_years_test() ->
+    Seconds = 189839836,
+    equalFloat(space_age:ageOn(earth, Seconds), 6.02),
+    equalFloat(space_age:ageOn(venus, Seconds), 9.78).
+
+age_in_mars_years_test() ->
+    Seconds = 2329871239,
+    equalFloat(space_age:ageOn(earth, Seconds), 73.83),
+    equalFloat(space_age:ageOn(mars, Seconds), 39.25).
+
+age_in_jupiter_years_test() ->
+    Seconds = 901876382,
+    equalFloat(space_age:ageOn(earth, Seconds), 28.58),
+    equalFloat(space_age:ageOn(jupiter, Seconds), 2.41).
+
+age_in_saturn_years_test() ->
+    Seconds = 3000000000,
+    equalFloat(space_age:ageOn(earth, Seconds), 95.06),
+    equalFloat(space_age:ageOn(saturn, Seconds), 3.23).
+
+age_in_uranus_years_test() ->
+    Seconds = 3210123456,
+    equalFloat(space_age:ageOn(earth, Seconds), 101.72),
+    equalFloat(space_age:ageOn(uranus, Seconds), 1.21).
+
+age_in_neptune_years_test() ->
+    Seconds = 8210123456,
+    equalFloat(space_age:ageOn(earth, Seconds), 260.16),
+    equalFloat(space_age:ageOn(neptune, Seconds), 1.58).
+
+equalFloat(A, B) ->
+    ?assertEqual(round(A,2), B).
+
+round(Number, Precision) ->
+    P = math:pow(10, Precision),
+    round(Number * P) / P.