Find robots

* add robotNamed : string -> cmd robot
* add chess knight challenge

In challenges, it's impossible to access the robot
by its assigned number. We do however name it.
Seems reasonable to add a way to get robot by its name.

data/scenarios/03Challenges/01-chess_horse.yaml

@@ -0,0 +1,70 @@
+name: Chess Knight
+description: In this quirky challenge, you move as the chess knight piece. Can you capture the enemy king?
+entities:
+  - name: goal
+    display:
+      attr: device
+      char: 'X'
+    description:
+    - |
+      Robots can use the 'move' command to move.
+      But they only 'turn' in cardinal directions. 
+
+      You are special. You are a knight. 
+
+      Go forth and capture the King!
+    properties: [portable]
+  - name: knownwater
+    display:
+      attr: water
+      char: ' '
+    description:
+    - An infinite ocean of water.
+    properties: [known, portable, growable, liquid]
+    growth: [0,0]
+win: |
+  try {
+    bloc <- as base {whereami};
+    king <- robotNamed "king";
+    kloc <- as king {whereami};
+    return (bloc == kloc)
+  } { return false }
+robots:
+  - name: horse
+    loc: [0,0]
+    dir: [2,-1]
+    devices:
+      - treads
+      - logger
+    inventory:
+      - [1, goal]
+    display:
+      char: '♘'
+  - name: king
+    loc: [7,-6]
+    dir: [0,0]
+    display:
+      char: '♚'
+world:
+  default: [ice, knownwater]
+  palette:
+    '.': [grass, null]
+    '#': [ice, null]
+    '┌': [stone, upper left corner]
+    '┐': [stone, upper right corner]
+    '└': [stone, lower left corner]
+    '┘': [stone, lower right corner]
+    '─': [stone, horizontal wall]
+    '│': [stone, vertical wall]
+  upperleft: [-1, 1]
+  map: |
+    ┌────────┐
+    │.#.#.#.#│
+    │#.#.#.#.│
+    │.#.#.#.#│
+    │#.#.#.#.│
+    │.#.#.#.#│
+    │#.#.#.#.│
+    │.#.#.#.#│
+    │#.#.#.#.│
+    └────────┘

src/Swarm/Game/Step.hs

@@ -206,6 +206,10 @@ updateEntityAt loc upd = zoomWorld (W.updateM @Int (W.locToCoords loc) upd)
 robotWithID :: (Has (State GameState) sig m) => RID -> m (Maybe Robot)
 robotWithID rid = use (robotMap . at rid)
 
+-- | Get the robot with a given name.
+robotWithName :: (Has (State GameState) sig m) => Text -> m (Maybe Robot)
+robotWithName rname = use (robotMap . to IM.elems . to (find $ \r -> r ^. robotName == rname))
+
 -- | Manhattan distance between world locations.
 manhattan :: V2 Int64 -> V2 Int64 -> Int64
 manhattan (V2 x1 y1) (V2 x2 y2) = abs (x1 - x2) + abs (y1 - y2)
@@ -969,6 +973,12 @@ execConst c vs s k = do
         -- Return the value returned by the hypothetical command.
         return $ Out v s k
       _ -> badConst
+    RobotNamed -> case vs of
+      [VString rname] -> do
+        r <- robotWithName rname >>= (`isJustOrFail` ["There is no robot named", rname])
+        let robotValue = VRobot (r ^. robotID)
+        return $ Out robotValue s k
+      _ -> badConst
     Say -> case vs of
       [VString msg] -> do
         rn <- use robotName -- XXX use robot name + ID

src/Swarm/Language/Capability.hs

@@ -268,6 +268,7 @@ constCaps =
     Drill -> [CDrill]
     -- Some God-like sensing abilities.
     As -> [CGod]
+    RobotNamed -> [CGod]
     -- String operations, which for now are enabled by CLog
     Format -> [CLog]
     Concat -> [CLog]

src/Swarm/Language/Syntax.hs

@@ -347,6 +347,8 @@ data Const
 
     -- | Run a command as if you were another robot.
     As
+  | -- | Find a robot by name.
+    RobotNamed
   deriving (Eq, Ord, Enum, Bounded, Data, Show)
 
 allConst :: [Const]
@@ -484,6 +486,7 @@ constInfo c = case c of
   Concat -> binaryOp "++" 6 R
   AppF -> binaryOp "$" 0 R
   As -> commandLow 2
+  RobotNamed -> commandLow 1
  where
   unaryOp s p side = ConstInfo {syntax = s, fixity = p, constMeta = ConstMUnOp side}
   binaryOp s p side = ConstInfo {syntax = s, fixity = p, constMeta = ConstMBinOp side}

src/Swarm/Language/Typecheck.hs

@@ -499,6 +499,7 @@ inferConst c = toU $ case c of
   Concat -> [tyQ| string -> string -> string |]
   AppF -> [tyQ| (a -> b) -> a -> b |]
   As -> [tyQ| robot -> {cmd a} -> cmd a |]
+  RobotNamed -> [tyQ| string -> cmd robot |]
  where
   cmpBinT = [tyQ| a -> a -> bool |]
   arithBinT = [tyQ| int -> int -> int |]