Given an age in seconds, calculate how old someone would be on:
So if you were told someone were 1,000,000,000 seconds old, you should be able to say that they're 31.69 Earth-years old.
If you're wondering why Pluto didn't make the cut, go watch this youtube video.
In this exercise, we provided the definition of the
algebric data type
named Planet
.
You need to implement the ageOn
function, that calculates how many
years old someone would be on a Planet
, given an age in seconds.
Your can use the provided signature if you are unsure about the types, but don't let it restrict your creativity:
ageOn :: Planet -> Float -> Float
For installation and learning resources, refer to the exercism help page.
To run the test suite, execute the following command:
stack test
No .cabal file found in directory
You are probably running an old stack version and need to upgrade it.
No compiler found, expected minor version match with...
Try running "stack setup" to install the correct GHC...
Just do as it says and it will download and install the correct compiler version:
stack setup
If you want to play with your solution in GHCi, just run the command:
stack ghci
The exercism/haskell repository on GitHub is the home for all of the Haskell exercises.
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Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=01
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
{-# OPTIONS_GHC -fno-warn-type-defaults #-}
{-# LANGUAGE RecordWildCards #-}
import Data.Foldable (for_)
import Data.Function (on)
import Test.Hspec (Spec, describe, it, shouldBe)
import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
import SpaceAge (Planet(..), ageOn)
main :: IO ()
main = hspecWith defaultConfig {configFastFail = True} specs
specs :: Spec
specs = describe "ageOn" $ for_ cases test
where
-- Here we used `fromIntegral`, `fromRational` and `toRational` to
-- generalize the test suite, allowing any function that takes a
-- `Planet` and a number, returning an instance of `Real`.
test Case{..} = it description $ expression `shouldBeAround` expected
where
expression = fromRational
. toRational
. ageOn planet
. fromIntegral
$ seconds
shouldBeAround = shouldBe `on` roundTo 2
roundTo n = (/ 10 ^ n) . fromIntegral . round . (* 10 ^ n)
data Case = Case { description :: String
, planet :: Planet
, seconds :: Integer
, expected :: Double
}
cases :: [Case]
cases = [ Case { description = "Earth"
, planet = Earth
, seconds = 1000000000
, expected = 31.69
}
, Case { description = "Mercury"
, planet = Mercury
, seconds = 2134835688
, expected = 280.88
}
, Case { description = "Venus"
, planet = Venus
, seconds = 189839836
, expected = 9.78
}
, Case { description = "Mars"
, planet = Mars
, seconds = 2329871239
, expected = 39.25
}
, Case { description = "Jupiter"
, planet = Jupiter
, seconds = 901876382
, expected = 2.41
}
, Case { description = "Saturn"
, planet = Saturn
, seconds = 3000000000
, expected = 3.23
}
, Case { description = "Uranus"
, planet = Uranus
, seconds = 3210123456
, expected = 1.21
}
, Case { description = "Neptune"
, planet = Neptune
, seconds = 8210123456
, expected = 1.58
}
]
module SpaceAge (Planet(..), ageOn) where
data Planet = Mercury
| Venus
| Earth
| Mars
| Jupiter
| Saturn
| Uranus
| Neptune
ageOn :: Planet -> Float -> Float
ageOn planet seconds = seconds / (rock planet * 31557600)
where rock Mercury = 0.2408467
rock Venus = 0.61519726
rock Earth = 1
rock Mars = 1.8808158
rock Jupiter = 11.862615
rock Saturn = 29.447498
rock Uranus = 84.016846
rock Neptune = 164.79132
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