39 lines
947 B
Elixir
39 lines
947 B
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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@type factors :: %{planet => float}
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@factors %{
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mercury: 0.2408467,
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venus: 0.61519726,
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earth: 1.0,
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mars: 1.8808158,
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jupiter: 11.862615,
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saturn: 29.447498,
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uranus: 84.016846,
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neptune: 164.79132
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}
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@seconds_in_year 31_557_600
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defguardp is_planet(planet) when is_map_key(@factors, planet)
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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 / (@factors[planet] * @seconds_in_year)}
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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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