Adds 5th concept step to tie it all together

exercises/concept/secrets/.docs/hints.md

@@ -19,6 +19,17 @@
 - [One of the bitwise functions][bitwise-and] clears bits where the bit in the mask is 0.
 - But, you may need to combine it with [another function][bitwise-complement] to clear bits where the mask is 1.
 
+## 5. Decrypt a message
+
+- Apply the other functions you wrote to the input in the following order, taking the output of one and using it as the input to the next one:
+
+1. `setBits`
+2. `flipBits`
+3. `shiftBack`
+4. `clearBits`
+
+For step 4, you'll need to convert the binary number with the 1st and 5th bits set (10001) to decimal.
+
 [bitwise-docs]: https://package.elm-lang.org/packages/elm/core/latest/Bitwise
 [bitwise-shiftRightZfBy]: https://package.elm-lang.org/packages/elm/core/latest/Bitwise#shiftRightZfBy
 [bitwise-or]: https://package.elm-lang.org/packages/elm/core/latest/Bitwise#or

exercises/concept/secrets/.docs/instructions.md

@@ -43,7 +43,7 @@ flipBits 23 157 --> 138
 
 ## 4. Clear specific bits
 
-Lastly, there are also certain bits that always decrypt to 0.
+There are also certain bits that always decrypt to 0.
 
 Implement the `clearBits` functions that takes a mask and a value.
 The bits in the `value` should be set to 0 where the bit in the mask is 1.
@@ -52,3 +52,17 @@ All other bits should be kept unchanged.
 ```elm
 clearBits 2 15 --> 13
 ```
+
+## 5. Decrypt a message
+
+Now that you have all the functions you need, you can decode your friend's message.
+Implement the `decrypt` function that performs the following operations:
+
+1. Set the bits from the year your friend was born (1996)
+2. Flip the result with the year that you first met (2009)
+3. Shift the bits back by the number of classes you take together (5)
+4. Clear the first and fifth bit.
+
+```elm
+decrypt 380182 -->
+```

exercises/concept/secrets/.meta/Exemplar.elm

@@ -1,4 +1,4 @@
-module Secrets exposing (clearBits, flipBits, setBits, shiftBack)
+module Secrets exposing (clearBits, flipBits, setBits, shiftBack, decrypt)
 
 import Bitwise
 
@@ -19,3 +19,11 @@ clearBits mask value =
     mask
         |> Bitwise.complement
         |> Bitwise.and value
+
+
+decrypt secret = 
+    secret
+    |> setBits 1996
+    |> flipBits 2009
+    |> shiftBack 5
+    |> clearBits 17

exercises/concept/secrets/src/Secrets.elm

@@ -1,4 +1,4 @@
-module Secrets exposing (clearBits, flipBits, setBits, shiftBack)
+module Secrets exposing (clearBits, decrypt, flipBits, setBits, shiftBack)
 
 
 shiftBack amount value =
@@ -15,3 +15,7 @@ flipBits mask value =
 
 clearBits mask value =
     Debug.todo "Please implement clearBits"
+
+
+decrypt secret =
+    Debug.todo "Please implement decrypt"

exercises/concept/secrets/tests/Tests.elm

@@ -48,4 +48,14 @@ tests =
                     Secrets.clearBits 240 90
                         |> Expect.equal 10
             ]
+        , describe "5"
+            [ test "Decrypt 12345" <|
+                \_ ->
+                    Secrets.decrypt 12345
+                        |> Expect.equal 384
+            , test "Decrypt 123456789" <|
+                \_ ->
+                    Secrets.decrypt 123456789
+                        |> Expect.equal 3857984
+            ]
         ]