93 lines
2.2 KiB
Markdown
93 lines
2.2 KiB
Markdown
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# Secret Handshake
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> There are 10 types of people in the world: Those who understand
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> binary, and those who don't.
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You and your fellow cohort of those in the "know" when it comes to
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binary decide to come up with a secret "handshake".
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```text
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1 = wink
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10 = double blink
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100 = close your eyes
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1000 = jump
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10000 = Reverse the order of the operations in the secret handshake.
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```
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Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
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Here's a couple of examples:
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Given the input 3, the function would return the array
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["wink", "double blink"] because 3 is 11 in binary.
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Given the input 19, the function would return the array
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["double blink", "wink"] because 19 is 10011 in binary.
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Notice that the addition of 16 (10000 in binary)
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has caused the array to be reversed.
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use Bitwise (or div/rem)
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If you use Bitwise, an easy way to see if a particular bit is set is to compare
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the binary AND (`&&&`) of a set of bits with the particular bit pattern you
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want to check, and determine if the result is the same as the pattern you're
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checking.
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Example:
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Flags: 0b11011
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Check: 0b11010
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Flags &&& Check: 0b11010 (All checked bits are set)
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Another:
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Flags: 0b11011
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Check: 0b10110
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Flags &&& Check: 0b10010 (Third bit not set)
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## Running tests
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Execute the tests with:
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```bash
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$ elixir secret_handshake_test.exs
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```
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### Pending tests
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In the test suites, all but the first test have been skipped.
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Once you get a test passing, you can unskip the next one by
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commenting out the relevant `@tag :pending` with a `#` symbol.
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For example:
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```elixir
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# @tag :pending
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test "shouting" do
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assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
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end
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```
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Or, you can enable all the tests by commenting out the
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`ExUnit.configure` line in the test suite.
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```elixir
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# ExUnit.configure exclude: :pending, trace: true
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```
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For more detailed information about the Elixir track, please
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see the [help page](http://exercism.io/languages/elixir).
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## Source
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Bert, in Mary Poppins [http://www.imdb.com/title/tt0058331/quotes/qt0437047](http://www.imdb.com/title/tt0058331/quotes/qt0437047)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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