davearonson's solution to Gigasecond on the Elixir track

Instructions

Test suite

Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Calculate the moment when someone has lived for 10^9 seconds.

A gigasecond is 10^9 (1,000,000,000) seconds.

Running tests

Execute the tests with:

$ elixir gigasecond_test.exs

Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant @tag :pending with a # symbol.

For example:

# @tag :pending
test "shouting" do
  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end

Or, you can enable all the tests by commenting out the ExUnit.configure line in the test suite.

# ExUnit.configure exclude: :pending, trace: true

For more detailed information about the Elixir track, please see the help page.

Source

Chapter 9 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=09

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

gigasecond_test.exs

if !System.get_env("EXERCISM_TEST_EXAMPLES") do
  Code.load_file("gigasecond.exs", __DIR__)
end

ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)

defmodule GigasecondTest do
  use ExUnit.Case

  # @tag :pending
  test "from 4/25/2011" do
    assert Gigasecond.from({{2011, 4, 25}, {0, 0, 0}}) == {{2043, 1, 1}, {1, 46, 40}}
  end

  @tag :pending
  test "from 6/13/1977" do
    assert Gigasecond.from({{1977, 6, 13}, {0, 0, 0}}) == {{2009, 2, 19}, {1, 46, 40}}
  end

  @tag :pending
  test "from 7/19/1959" do
    assert Gigasecond.from({{1959, 7, 19}, {0, 0, 0}}) == {{1991, 3, 27}, {1, 46, 40}}
  end

  @tag :pending
  test "yourself" do
    # customize these values for yourself
    # your_birthday = {{year1, month1, day1}, {0, 0, 0}}
    # assert Gigasecond.from(your_birthday) == {{year2, month2, day2}, {hours, minutes, seconds}}
  end
end

defmodule Gigasecond do
  @doc """
  Calculate a date one billion seconds after an input date.
  """

  @one_billion 1_000_000_000

  @spec from({{pos_integer, pos_integer, pos_integer}, {pos_integer, pos_integer, pos_integer}}) :: :calendar.datetime
  # def from({{year, month, day}, {hours, minutes, seconds}}) do
    def from(time) do
      ((time|> :calendar.datetime_to_gregorian_seconds) + @one_billion)
      |> :calendar.gregorian_seconds_to_datetime
    end
end

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davearonson's solution

to Gigasecond in the Elixir Track