36 lines
1.0 KiB
Elixir
36 lines
1.0 KiB
Elixir
defmodule SpaceAge do
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@type planet ::
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:mercury
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| :venus
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| :earth
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| :mars
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| :jupiter
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| :saturn
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| :uranus
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| :neptune
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@planets ~w(mercury venus earth mars jupiter saturn uranus neptune)a
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defguardp is_planet(planet) when planet in @planets
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defp factor(:mercury), do: 0.2408467
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defp factor(:venus), do: 0.61519726
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defp factor(:earth), do: 1.0
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defp factor(:mars), do: 1.8808158
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defp factor(:jupiter), do: 11.862615
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defp factor(:saturn), do: 29.447498
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defp factor(:uranus), do: 84.016846
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defp factor(:neptune), do: 164.79132
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@doc """
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Return the number of years a person that has lived for 'seconds' seconds is
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aged on 'planet', or an error if 'planet' is not a planet.
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"""
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@spec age_on(planet, pos_integer) :: {:ok, float} | {:error, String.t()}
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def age_on(planet, seconds) when is_planet(planet),
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do: {:ok, seconds / (factor(planet) * 31_557_600)}
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def age_on(_planet, _seconds),
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do: {:error, "not a planet"}
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end
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