# shmibs's solution

## to Meetup in the Elixir Track

Published at Jul 13 2018 · 0 comments
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 date of meetups.

Typically meetups happen on the same day of the week. In this exercise, you will take a description of a meetup date, and return the actual meetup date.

Examples of general descriptions are:

• The first Monday of January 2017
• The third Tuesday of January 2017
• The wednesteenth of January 2017
• The last Thursday of January 2017

The descriptors you are expected to parse are: first, second, third, fourth, fifth, last, monteenth, tuesteenth, wednesteenth, thursteenth, friteenth, saturteenth, sunteenth

Note that "monteenth", "tuesteenth", etc are all made up words. There was a meetup whose members realized that there are exactly 7 numbered days in a month that end in '-teenth'. Therefore, one is guaranteed that each day of the week (Monday, Tuesday, ...) will have exactly one date that is named with '-teenth' in every month.

Given examples of a meetup dates, each containing a month, day, year, and descriptor calculate the date of the actual meetup. For example, if given "The first Monday of January 2017", the correct meetup date is 2017/1/2.

## Running tests

Execute the tests with:

``````\$ elixir meetup_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

Jeremy Hinegardner mentioned a Boulder meetup that happens on the Wednesteenth of every month https://twitter.com/copiousfreetime

## Submitting Incomplete Solutions

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

### meetup_test.exs

``````if !System.get_env("EXERCISM_TEST_EXAMPLES") do
end

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

defmodule MeetupTest do
use ExUnit.Case

# @tag :pending
test "monteenth of may 2013" do
assert Meetup.meetup(2013, 5, :monday, :teenth) == {2013, 5, 13}
end

@tag :pending
test "monteenth of august 2013" do
assert Meetup.meetup(2013, 8, :monday, :teenth) == {2013, 8, 19}
end

@tag :pending
test "monteenth of september 2013" do
assert Meetup.meetup(2013, 9, :monday, :teenth) == {2013, 9, 16}
end

@tag :pending
test "tuesteenth of march 2013" do
assert Meetup.meetup(2013, 3, :tuesday, :teenth) == {2013, 3, 19}
end

@tag :pending
test "tuesteenth of april 2013" do
assert Meetup.meetup(2013, 4, :tuesday, :teenth) == {2013, 4, 16}
end

@tag :pending
test "tuesteenth of august 2013" do
assert Meetup.meetup(2013, 8, :tuesday, :teenth) == {2013, 8, 13}
end

@tag :pending
test "wednesteenth of january 2013" do
assert Meetup.meetup(2013, 1, :wednesday, :teenth) == {2013, 1, 16}
end

@tag :pending
test "wednesteenth of february 2013" do
assert Meetup.meetup(2013, 2, :wednesday, :teenth) == {2013, 2, 13}
end

@tag :pending
test "wednesteenth of june 2013" do
assert Meetup.meetup(2013, 6, :wednesday, :teenth) == {2013, 6, 19}
end

@tag :pending
test "thursteenth of may 2013" do
assert Meetup.meetup(2013, 5, :thursday, :teenth) == {2013, 5, 16}
end

@tag :pending
test "thursteenth of june 2013" do
assert Meetup.meetup(2013, 6, :thursday, :teenth) == {2013, 6, 13}
end

@tag :pending
test "thursteenth of september 2013" do
assert Meetup.meetup(2013, 9, :thursday, :teenth) == {2013, 9, 19}
end

@tag :pending
test "friteenth of april 2013" do
assert Meetup.meetup(2013, 4, :friday, :teenth) == {2013, 4, 19}
end

@tag :pending
test "friteenth of august 2013" do
assert Meetup.meetup(2013, 8, :friday, :teenth) == {2013, 8, 16}
end

@tag :pending
test "friteenth of september 2013" do
assert Meetup.meetup(2013, 9, :friday, :teenth) == {2013, 9, 13}
end

@tag :pending
test "saturteenth of february 2013" do
assert Meetup.meetup(2013, 2, :saturday, :teenth) == {2013, 2, 16}
end

@tag :pending
test "saturteenth of april 2013" do
assert Meetup.meetup(2013, 4, :saturday, :teenth) == {2013, 4, 13}
end

@tag :pending
test "saturteenth of october 2013" do
assert Meetup.meetup(2013, 10, :saturday, :teenth) == {2013, 10, 19}
end

@tag :pending
test "sunteenth of may 2013" do
assert Meetup.meetup(2013, 5, :sunday, :teenth) == {2013, 5, 19}
end

@tag :pending
test "sunteenth of june 2013" do
assert Meetup.meetup(2013, 6, :sunday, :teenth) == {2013, 6, 16}
end

@tag :pending
test "sunteenth of october 2013" do
assert Meetup.meetup(2013, 10, :sunday, :teenth) == {2013, 10, 13}
end

@tag :pending
test "first monday of march 2013" do
assert Meetup.meetup(2013, 3, :monday, :first) == {2013, 3, 4}
end

@tag :pending
test "first monday of april 2013" do
assert Meetup.meetup(2013, 4, :monday, :first) == {2013, 4, 1}
end

@tag :pending
test "first tuesday of may 2013" do
assert Meetup.meetup(2013, 5, :tuesday, :first) == {2013, 5, 7}
end

@tag :pending
test "first tuesday of june 2013" do
assert Meetup.meetup(2013, 6, :tuesday, :first) == {2013, 6, 4}
end

@tag :pending
test "first wednesday of july 2013" do
assert Meetup.meetup(2013, 7, :wednesday, :first) == {2013, 7, 3}
end

@tag :pending
test "first wednesday of august 2013" do
assert Meetup.meetup(2013, 8, :wednesday, :first) == {2013, 8, 7}
end

@tag :pending
test "first thursday of september 2013" do
assert Meetup.meetup(2013, 9, :thursday, :first) == {2013, 9, 5}
end

@tag :pending
test "first thursday of october 2013" do
assert Meetup.meetup(2013, 10, :thursday, :first) == {2013, 10, 3}
end

@tag :pending
test "first friday of november 2013" do
assert Meetup.meetup(2013, 11, :friday, :first) == {2013, 11, 1}
end

@tag :pending
test "first friday of december 2013" do
assert Meetup.meetup(2013, 12, :friday, :first) == {2013, 12, 6}
end

@tag :pending
test "first saturday of january 2013" do
assert Meetup.meetup(2013, 1, :saturday, :first) == {2013, 1, 5}
end

@tag :pending
test "first saturday of february 2013" do
assert Meetup.meetup(2013, 2, :saturday, :first) == {2013, 2, 2}
end

@tag :pending
test "first sunday of march 2013" do
assert Meetup.meetup(2013, 3, :sunday, :first) == {2013, 3, 3}
end

@tag :pending
test "first sunday of april 2013" do
assert Meetup.meetup(2013, 4, :sunday, :first) == {2013, 4, 7}
end

@tag :pending
test "second monday of march 2013" do
assert Meetup.meetup(2013, 3, :monday, :second) == {2013, 3, 11}
end

@tag :pending
test "second monday of april 2013" do
assert Meetup.meetup(2013, 4, :monday, :second) == {2013, 4, 8}
end

@tag :pending
test "second tuesday of may 2013" do
assert Meetup.meetup(2013, 5, :tuesday, :second) == {2013, 5, 14}
end

@tag :pending
test "second tuesday of june 2013" do
assert Meetup.meetup(2013, 6, :tuesday, :second) == {2013, 6, 11}
end

@tag :pending
test "second wednesday of july 2013" do
assert Meetup.meetup(2013, 7, :wednesday, :second) == {2013, 7, 10}
end

@tag :pending
test "second wednesday of august 2013" do
assert Meetup.meetup(2013, 8, :wednesday, :second) == {2013, 8, 14}
end

@tag :pending
test "second thursday of september 2013" do
assert Meetup.meetup(2013, 9, :thursday, :second) == {2013, 9, 12}
end

@tag :pending
test "second thursday of october 2013" do
assert Meetup.meetup(2013, 10, :thursday, :second) == {2013, 10, 10}
end

@tag :pending
test "second friday of november 2013" do
assert Meetup.meetup(2013, 11, :friday, :second) == {2013, 11, 8}
end

@tag :pending
test "second friday of december 2013" do
assert Meetup.meetup(2013, 12, :friday, :second) == {2013, 12, 13}
end

@tag :pending
test "second saturday of january 2013" do
assert Meetup.meetup(2013, 1, :saturday, :second) == {2013, 1, 12}
end

@tag :pending
test "second saturday of february 2013" do
assert Meetup.meetup(2013, 2, :saturday, :second) == {2013, 2, 9}
end

@tag :pending
test "second sunday of march 2013" do
assert Meetup.meetup(2013, 3, :sunday, :second) == {2013, 3, 10}
end

@tag :pending
test "second sunday of april 2013" do
assert Meetup.meetup(2013, 4, :sunday, :second) == {2013, 4, 14}
end

@tag :pending
test "third monday of march 2013" do
assert Meetup.meetup(2013, 3, :monday, :third) == {2013, 3, 18}
end

@tag :pending
test "third monday of april 2013" do
assert Meetup.meetup(2013, 4, :monday, :third) == {2013, 4, 15}
end

@tag :pending
test "third tuesday of may 2013" do
assert Meetup.meetup(2013, 5, :tuesday, :third) == {2013, 5, 21}
end

@tag :pending
test "third tuesday of june 2013" do
assert Meetup.meetup(2013, 6, :tuesday, :third) == {2013, 6, 18}
end

@tag :pending
test "third wednesday of july 2013" do
assert Meetup.meetup(2013, 7, :wednesday, :third) == {2013, 7, 17}
end

@tag :pending
test "third wednesday of august 2013" do
assert Meetup.meetup(2013, 8, :wednesday, :third) == {2013, 8, 21}
end

@tag :pending
test "third thursday of september 2013" do
assert Meetup.meetup(2013, 9, :thursday, :third) == {2013, 9, 19}
end

@tag :pending
test "third thursday of october 2013" do
assert Meetup.meetup(2013, 10, :thursday, :third) == {2013, 10, 17}
end

@tag :pending
test "third friday of november 2013" do
assert Meetup.meetup(2013, 11, :friday, :third) == {2013, 11, 15}
end

@tag :pending
test "third friday of december 2013" do
assert Meetup.meetup(2013, 12, :friday, :third) == {2013, 12, 20}
end

@tag :pending
test "third saturday of january 2013" do
assert Meetup.meetup(2013, 1, :saturday, :third) == {2013, 1, 19}
end

@tag :pending
test "third saturday of february 2013" do
assert Meetup.meetup(2013, 2, :saturday, :third) == {2013, 2, 16}
end

@tag :pending
test "third sunday of march 2013" do
assert Meetup.meetup(2013, 3, :sunday, :third) == {2013, 3, 17}
end

@tag :pending
test "third sunday of april 2013" do
assert Meetup.meetup(2013, 4, :sunday, :third) == {2013, 4, 21}
end

@tag :pending
test "fourth monday of march 2013" do
assert Meetup.meetup(2013, 3, :monday, :fourth) == {2013, 3, 25}
end

@tag :pending
test "fourth monday of april 2013" do
assert Meetup.meetup(2013, 4, :monday, :fourth) == {2013, 4, 22}
end

@tag :pending
test "fourth tuesday of may 2013" do
assert Meetup.meetup(2013, 5, :tuesday, :fourth) == {2013, 5, 28}
end

@tag :pending
test "fourth tuesday of june 2013" do
assert Meetup.meetup(2013, 6, :tuesday, :fourth) == {2013, 6, 25}
end

@tag :pending
test "fourth wednesday of july 2013" do
assert Meetup.meetup(2013, 7, :wednesday, :fourth) == {2013, 7, 24}
end

@tag :pending
test "fourth wednesday of august 2013" do
assert Meetup.meetup(2013, 8, :wednesday, :fourth) == {2013, 8, 28}
end

@tag :pending
test "fourth thursday of september 2013" do
assert Meetup.meetup(2013, 9, :thursday, :fourth) == {2013, 9, 26}
end

@tag :pending
test "fourth thursday of october 2013" do
assert Meetup.meetup(2013, 10, :thursday, :fourth) == {2013, 10, 24}
end

@tag :pending
test "fourth friday of november 2013" do
assert Meetup.meetup(2013, 11, :friday, :fourth) == {2013, 11, 22}
end

@tag :pending
test "fourth friday of december 2013" do
assert Meetup.meetup(2013, 12, :friday, :fourth) == {2013, 12, 27}
end

@tag :pending
test "fourth saturday of january 2013" do
assert Meetup.meetup(2013, 1, :saturday, :fourth) == {2013, 1, 26}
end

@tag :pending
test "fourth saturday of february 2013" do
assert Meetup.meetup(2013, 2, :saturday, :fourth) == {2013, 2, 23}
end

@tag :pending
test "fourth sunday of march 2013" do
assert Meetup.meetup(2013, 3, :sunday, :fourth) == {2013, 3, 24}
end

@tag :pending
test "fourth sunday of april 2013" do
assert Meetup.meetup(2013, 4, :sunday, :fourth) == {2013, 4, 28}
end

@tag :pending
test "last monday of march 2013" do
assert Meetup.meetup(2013, 3, :monday, :last) == {2013, 3, 25}
end

@tag :pending
test "last monday of april 2013" do
assert Meetup.meetup(2013, 4, :monday, :last) == {2013, 4, 29}
end

@tag :pending
test "last tuesday of may 2013" do
assert Meetup.meetup(2013, 5, :tuesday, :last) == {2013, 5, 28}
end

@tag :pending
test "last tuesday of june 2013" do
assert Meetup.meetup(2013, 6, :tuesday, :last) == {2013, 6, 25}
end

@tag :pending
test "last wednesday of july 2013" do
assert Meetup.meetup(2013, 7, :wednesday, :last) == {2013, 7, 31}
end

@tag :pending
test "last wednesday of august 2013" do
assert Meetup.meetup(2013, 8, :wednesday, :last) == {2013, 8, 28}
end

@tag :pending
test "last thursday of september 2013" do
assert Meetup.meetup(2013, 9, :thursday, :last) == {2013, 9, 26}
end

@tag :pending
test "last thursday of october 2013" do
assert Meetup.meetup(2013, 10, :thursday, :last) == {2013, 10, 31}
end

@tag :pending
test "last friday of november 2013" do
assert Meetup.meetup(2013, 11, :friday, :last) == {2013, 11, 29}
end

@tag :pending
test "last friday of december 2013" do
assert Meetup.meetup(2013, 12, :friday, :last) == {2013, 12, 27}
end

@tag :pending
test "last saturday of january 2013" do
assert Meetup.meetup(2013, 1, :saturday, :last) == {2013, 1, 26}
end

@tag :pending
test "last saturday of february 2013" do
assert Meetup.meetup(2013, 2, :saturday, :last) == {2013, 2, 23}
end

@tag :pending
test "last sunday of march 2013" do
assert Meetup.meetup(2013, 3, :sunday, :last) == {2013, 3, 31}
end

@tag :pending
test "last sunday of april 2013" do
assert Meetup.meetup(2013, 4, :sunday, :last) == {2013, 4, 28}
end
end``````
``````defmodule Meetup do
@moduledoc """
Calculate meetup dates.
"""

@type weekday ::
:monday | :tuesday | :wednesday
| :thursday | :friday | :saturday | :sunday

@type schedule :: :first | :second | :third | :fourth | :last | :teenth

@wd2num %{
monday: 1, tuesday: 2, wednesday: 3, thursday: 4,
friday: 5, saturday: 6, sunday: 7
}

@doc """
Calculate a meetup date.

The schedule is in which week (1..4, last or "teenth") the meetup date should
fall.
"""
@spec meetup(pos_integer, pos_integer, weekday, schedule) :: :calendar.date
def meetup(y, m, wd, :first),  do: meetup_sub(y, m, wd, 1..7)
def meetup(y, m, wd, :second), do: meetup_sub(y, m, wd, 8..14)
def meetup(y, m, wd, :third),  do: meetup_sub(y, m, wd, 15..21)
def meetup(y, m, wd, :fourth), do: meetup_sub(y, m, wd, 22..28)
def meetup(y, m, wd, :teenth), do: meetup_sub(y, m, wd, 13..19)
def meetup(y, m, wd, :last) do
meetup_sub(y, m, wd, ((last(y,m)-6)..last(y,m)) )
end

defp last(y, m), do: :calendar.last_day_of_the_month y, m

defp meetup_sub(y, m, wd, range) do
d = Enum.find(range, &(@wd2num[wd] == :calendar.day_of_the_week y, m, &1) )
{y, m, d}
end

end``````