sambeckingham's solution to Gigasecond on the Elm track

Instructions

Test suite

Solution

Given a moment, determine the moment that would be after a gigasecond has passed.

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

Elm Installation

Refer to the Installing Elm page for information about installing elm.

Writing the Code

The code you have to write is located inside the src/ directory of the exercise. Elm automatically installs packages dependencies the first time you run the tests so we can start by running the tests from the exercise directory with:

$ elm-test

To automatically run tests again when you save changes:

$ elm-test --watch

As you work your way through the tests suite in the file tests/Tests.elm, be sure to remove the skip <| calls from each test until you get them all passing!

Source

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

Submitting Incomplete Solutions

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

Tests.elm

module Tests exposing (tests)

import Expect
import Gigasecond exposing (add)
import Iso8601
import Parser
import Test exposing (..)
import Time


tests : Test
tests =
    describe "Gigasecond"
        [ describe "add"
            [ test "2011-04-25" <|
                \() ->
                    Expect.equal "2043-01-01T01:46:40.000Z"
                        (gigasecond "2011-04-25")
            , skip <|
                test "1977-06-13" <|
                    \() ->
                        Expect.equal "2009-02-19T01:46:40.000Z"
                            (gigasecond "1977-06-13")
            , skip <|
                test "1959-07-19" <|
                    \() ->
                        Expect.equal "1991-03-27T01:46:40.000Z"
                            (gigasecond "1959-07-19")
            , skip <|
                test "full time specified" <|
                    \() ->
                        Expect.equal "2046-10-02T23:46:40.000Z"
                            (gigasecond "2015-01-24T22:00:00.000Z")
            , skip <|
                test "full time with day roll-over" <|
                    \() ->
                        Expect.equal "2046-10-03T01:46:39.000Z"
                            (gigasecond "2015-01-24T23:59:59.000Z")
            ]
        ]


gigasecond : String -> String
gigasecond date =
    case Iso8601.toTime date of
        Ok posix ->
            posix
                |> Gigasecond.add
                |> Iso8601.fromTime

        _ ->
            ""

module Gigasecond exposing (add)

import Time


add : Time.Posix -> Time.Posix
add timestamp =
    (Time.posixToMillis
        >> (+) gigasecondInMs
        >> Time.millisToPosix
    )
        timestamp


gigasecondInMs : Int
gigasecondInMs =
    10 ^ 12

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sambeckingham's solution

to Gigasecond in the Elm Track