Add robot name exercise

config.json

@@ -675,6 +675,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "robot-name",
+        "name": "Robot Name",
+        "uuid": "88eac1aa-a4ae-405a-88ab-0dedd5ac7ae2",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "acronym",
         "name": "Acronym",

config/generator_macros.j2

@@ -29,6 +29,8 @@ app [main] {
     json: "https://github.com/lukewilliamboswell/roc-json/releases/download/0.10.2/FH4N0Sw-JSFXJfG3j54VEDPtXOoN-6I9v_IA8S18IGk.tar.br"
     {%- elif name == "parser" -%}
     parser: "https://github.com/lukewilliamboswell/roc-parser/releases/download/0.7.2/1usTzOOACTpnkarBX0ED3gFESzR4ROdAlt1Llf4WFzo.tar.br"
+    {%- elif name == "rand" -%}
+    rand: "https://github.com/lukewilliamboswell/roc-random/releases/download/0.3.0/hPlOciYUhWMU7BefqNzL89g84-30fTE6l2_6Y3cxIcE.tar.br"
     {%- endif -%}
 {%- endfor -%}
 {%- endif %}

exercises/practice/robot-name/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+Manage robot factory settings.
+
+When a robot comes off the factory floor, it has no name.
+
+The first time you turn on a robot, a random name is generated in the format of two uppercase letters followed by three digits, such as RX837 or BC811.
+
+Every once in a while we need to reset a robot to its factory settings, which means that its name gets wiped.
+The next time you ask, that robot will respond with a new random name.
+
+The names must be random: they should not follow a predictable sequence.
+Using random names means a risk of collisions.
+Your solution must ensure that every existing robot has a unique name.

exercises/practice/robot-name/.meta/Example.roc

@@ -0,0 +1,89 @@
+module [createFactory, createRobot, boot, reset, getName, getFactory]
+
+import rand.Random
+
+## A factory is used to create robots, and hold state such as the existing robot
+## names and the current random state
+Factory := {
+    existingNames : Set Str,
+    state : Random.State,
+}
+
+## A robot must either have no name or a name composed of two letters followed
+## by three digits
+Robot := {
+    maybeName : Result Str [NoName],
+    factory : Factory,
+}
+
+createFactory : { seed : U32 } -> Factory
+createFactory = \{ seed } ->
+    @Factory { state: Random.seed seed, existingNames: Set.empty {} }
+
+createRobot : Factory -> Robot
+createRobot = \factory ->
+    @Robot { maybeName: Err NoName, factory }
+
+boot : Robot -> Robot
+boot = \robot ->
+    when robot |> getName is
+        Ok _ -> robot
+        Err NoName -> robot |> generateRandomName
+
+reset : Robot -> Robot
+reset = \robot ->
+    resetRobot =
+        when robot |> getName is
+            Err NoName -> robot
+            Ok nameToRemove ->
+                factory = robot |> getFactory |> removeName nameToRemove
+                @Robot { maybeName: Err NoName, factory }
+
+    resetRobot |> boot
+
+getName : Robot -> Result Str [NoName]
+getName = \@Robot { maybeName } ->
+    maybeName
+
+getFactory : Robot -> Factory
+getFactory = \@Robot { factory } ->
+    factory
+
+generateRandomName : Robot -> Robot
+generateRandomName = \@Robot { maybeName, factory } ->
+    (@Factory { state, existingNames }) = factory
+    { updatedState, string: twoLetters } = randomString { state, generator: Random.boundedU32 'A' 'Z', length: 2 }
+    { updatedState: updatedState2, string: threeDigits } = randomString { state: updatedState, generator: Random.boundedU32 '0' '9', length: 3 }
+    possibleName = "$(twoLetters)$(threeDigits)"
+
+    if existingNames |> Set.contains possibleName then
+        numberOfPossibleNames = 26 * 26 * 10 * 10 * 10
+        if existingNames |> Set.len == numberOfPossibleNames then
+            # better crash than run into an infinite loop
+            crash "Too many robots, we have run out of possible names!"
+        else
+            updatedFactory = @Factory { existingNames, state: updatedState2 }
+            generateRandomName (@Robot { maybeName, factory: updatedFactory })
+    else
+        updatedFactory = @Factory {
+            existingNames: existingNames |> Set.insert possibleName,
+            state: updatedState2,
+        }
+        @Robot { maybeName: Ok possibleName, factory: updatedFactory }
+
+removeName : Factory, Str -> Factory
+removeName = \@Factory { state, existingNames }, robotName ->
+    @Factory { state, existingNames: existingNames |> Set.remove robotName }
+
+randomString : { state : Random.State, generator : Random.Generator U32, length : U64 } -> { updatedState : Random.State, string : Str }
+randomString = \{ state, generator, length } ->
+    List.range { start: At 0, end: Before length }
+    |> List.walk { state, characters: [] } \walk, _ ->
+        random = generator walk.state
+        updatedState = random.state
+        characters = walk.characters |> List.append (random.value |> Num.toU8)
+        { state: updatedState, characters }
+    |> \{ state: updatedState, characters } ->
+        when characters |> Str.fromUtf8 is
+            Ok string -> { updatedState, string }
+            Err (BadUtf8 _ _) -> crash "Unreachable: characters are all ASCII"

exercises/practice/robot-name/.meta/config.json

@@ -0,0 +1,18 @@
+{
+  "authors": [
+    "ageron"
+  ],
+  "files": {
+    "solution": [
+      "RobotName.roc"
+    ],
+    "test": [
+      "robot-name-test.roc"
+    ],
+    "example": [
+      ".meta/Example.roc"
+    ]
+  },
+  "blurb": "Manage robot factory settings.",
+  "source": "A debugging session with Paul Blackwell at gSchool."
+}

exercises/practice/robot-name/RobotName.roc

@@ -0,0 +1,47 @@
+module [createFactory, createRobot, boot, reset, getName, getFactory]
+
+import rand.Random
+
+## A factory is used to create robots, and hold state such as the existing robot
+## names and the current random state
+Factory := {
+    # TODO: change this opaque type however you need
+    todo1 : U64,
+    todo2 : U64,
+    todo3 : U64,
+    # etc.
+}
+
+## A robot must either have no name or a name composed of two letters followed
+## by three digits
+Robot := {
+    # TODO: change this opaque type however you need
+    todo4 : U64,
+    todo5 : U64,
+    todo6 : U64,
+    # etc.
+}
+
+createFactory : { seed : U32 } -> Factory
+createFactory = \{ seed } ->
+    crash "Please implement the 'createFactory' function"
+
+createRobot : Factory -> Robot
+createRobot = \factory ->
+    crash "Please implement the 'createRobot' function"
+
+boot : Robot -> Robot
+boot = \robot ->
+    crash "Please implement the 'boot' function"
+
+reset : Robot -> Robot
+reset = \robot ->
+    crash "Please implement the 'reset' function"
+
+getName : Robot -> Result Str _
+getName = \robot ->
+    crash "Please implement the 'getName' function"
+
+getFactory : Robot -> Factory
+getFactory = \robot ->
+    crash "Please implement the 'getFactory' function"