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exercism fetch elixir secret-handshake

Secret Handshake

There are 10 types of people in the world: Those who understand binary, and those who don't.

You and your fellow cohort of those in the "know" when it comes to binary decide to come up with a secret "handshake".

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1 = wink
10 = double blink
100 = close your eyes
1000 = jump


10000 = Reverse the order of the operations in the secret handshake.

Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.

Here's a couple of examples:

Given the input 3, the function would return the array ["wink", "double blink"] because 3 is 11 in binary.

Given the input 19, the function would return the array ["double blink", "wink"] because 19 is 10011 in binary. Notice that the addition of 16 (10000 in binary) has caused the array to be reversed.

use Bitwise (or div/rem)

If you use Bitwise, an easy way to see if a particular bit is set is to compare the binary AND (&&&) of a set of bits with the particular bit pattern you want to check, and determine if the result is the same as the pattern you're checking.

Example:

Flags: 0b11011 Check: 0b11010

Flags &&& Check: 0b11010 (All checked bits are set)

Another:

Flags: 0b11011 Check: 0b10110

Flags &&& Check: 0b10010 (Third bit not set)

Running tests

Execute the tests with:

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$ elixir secret_handshake_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:

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# @tag :pending
test "wink for 1" do
  assert SecretHandshake.commands(1) == ["wink"]
end

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

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

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

Source

Bert, in Mary Poppins http://www.imdb.com/character/ch0011238/quotes

Submitting Incomplete Solutions

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