Update stub and example

exercises/practice/robot-simulator/.meta/example.arr

@@ -0,0 +1,44 @@
+use context essentials2020
+
+provide-types *
+
+include string-dict
+
+data Axis: axis(label, left, right) end
+
+cardinal_axes = [string-dict:
+  'north', axis('north', 'west', 'east'),
+  'south', axis('south', 'east', 'west'),
+  'east', axis('east', 'north','south'),
+  'west', axis('west','south', 'north'),
+]
+
+data Robot:
+  | robot(x :: NumInteger, y :: NumInteger, direction :: String) with:
+    method move(self, directions :: String) -> Robot:
+      foldl(
+        lam(acc, elt):
+          direction = 
+            ask:
+              | elt == 'L' then: cardinal_axes.get-value(self.direction).left
+              | elt == 'R' then: cardinal_axes.get-value(self.direction).right
+              | otherwise: self.direction
+            end
+          {x; y} =
+            if elt == 'A':
+              ask:
+                | direction == 'north' then: {acc.x; acc.y + 1}
+                | direction == 'south' then: {acc.x; acc.y - 1}
+                | direction == 'east' then: {acc.x + 1; acc.y}
+                | direction == 'west' then: {acc.x - 1; acc.y}
+              end
+            else:
+              {acc.x; acc.y}
+            end
+
+          robot(x, y, direction)
+        end,
+        self,
+        string-explode(directions))
+  end
+end

exercises/practice/robot-simulator/robot-simulator.arr

@@ -2,41 +2,8 @@ use context essentials2020
 
 provide-types *
 
-
-CARDINAL_DIRECTIONS = [list:
-  'north',
-  'east',
-  'south',
-  'west'
-]
-
-
 data Robot:
-  | robot(x :: NumInteger, y :: NumInteger, direction :: String) with:
-  method move(self, directions :: String) -> Robot:
-    foldl(
-        lam(acc, elt):
-            cases (String) elt:
-                | 'L' =>
-                    new-direction = ''
-                    robot(acc.x, acc.y, new-direction)
-                | 'R' => 
-                    new-direction = ''
-                    robot(acc.x, acc.y, new-direction)
-                | 'A' =>
-                    cases (String) acc.direction:
-                        | 'north'
-                            robot(0, acc.y + 1, self.direction)
-                        | 'east'
-                            robot(acc.x + 1, 0, self.direction)
-                        | 'south'
-                            robot(0, acc.y - 1, self.direction)
-                        | 'west'
-                            robot(acc.x - 1, 0, self.direction)
-                    end
-        end
-    end,
-    self,
-    string-explode(directions))
+  | robot(x :: NumInteger, y :: NumInteger, direction :: String)
+    ...
   end
 end