Robot simulator for Racket

config.json

@@ -670,6 +670,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 2
+      },
+      {
+        "slug": "robot-simulator",
+        "name": "Robot Simulator",
+        "uuid": "0abd9912-29e0-4eef-bd7d-0a17a9d3bfe3",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
       }
     ]
   },

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

@@ -0,0 +1,25 @@
+# Instructions
+
+Write a robot simulator.
+
+A robot factory's test facility needs a program to verify robot movements.
+
+The robots have three possible movements:
+
+- turn right
+- turn left
+- advance
+
+Robots are placed on a hypothetical infinite grid, facing a particular direction (north, east, south, or west) at a set of {x,y} coordinates,
+e.g., {3,8}, with coordinates increasing to the north and east.
+
+The robot then receives a number of instructions, at which point the testing facility verifies the robot's new position, and in which direction it is pointing.
+
+- The letter-string "RAALAL" means:
+  - Turn right
+  - Advance twice
+  - Turn left
+  - Advance once
+  - Turn left yet again
+- Say a robot starts at {7, 3} facing north.
+  Then running this stream of instructions should leave it at {9, 4} facing west.

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

@@ -0,0 +1,16 @@
+{
+  "authors": ["blakelewis"],
+  "files": {
+    "solution": [
+      "robot-simulator.rkt"
+    ],
+    "test": [
+      "robot-simulator-test.rkt"
+    ],
+    "example": [
+      ".meta/example.rkt"
+    ]
+  },
+  "blurb": "Write a robot simulator.",
+  "source": "Inspired by an interview question at a famous company."
+}

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

@@ -0,0 +1,34 @@
+#lang racket
+
+(provide robot%)
+
+(define dirs '(north east south west))
+(define step (hash 'north '(0 1) 'east '(1 0) 'south '(0 -1) 'west '(-1 0)))
+
+(define robot%
+  (class object%
+    (super-new)
+    (init-field [position '(0 0)]
+                [direction 'north])
+
+    (define (turn t)
+      (let* ([old-dir (index-of dirs direction)]
+             [new-dir (modulo (+ old-dir t) 4)])
+        (set! direction (list-ref dirs new-dir))))
+
+    (define (move-step point delta)
+      (let ([x (+ (car point) (car delta))]
+            [y (+ (cadr point) (cadr delta))])
+        (list x y)))
+
+    (define (advance)
+      (let ([s (hash-ref step direction)])
+        (set! position (move-step position s))))
+
+    (define/public (move instructions)
+      (for ([cmd (in-string instructions)])
+        (cond [(eq? cmd #\L) (turn -1)]
+              [(eq? cmd #\R) (turn 1)]
+              [(eq? cmd #\A) (advance)])))))
+
+

exercises/practice/robot-simulator/.meta/tests.toml

@@ -0,0 +1,64 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[c557c16d-26c1-4e06-827c-f6602cd0785c]
+description = "Create robot -> at origin facing north"
+
+[bf0dffce-f11c-4cdb-8a5e-2c89d8a5a67d]
+description = "Create robot -> at negative position facing south"
+
+[8cbd0086-6392-4680-b9b9-73cf491e67e5]
+description = "Rotating clockwise -> changes north to east"
+
+[8abc87fc-eab2-4276-93b7-9c009e866ba1]
+description = "Rotating clockwise -> changes east to south"
+
+[3cfe1b85-bbf2-4bae-b54d-d73e7e93617a]
+description = "Rotating clockwise -> changes south to west"
+
+[5ea9fb99-3f2c-47bd-86f7-46b7d8c3c716]
+description = "Rotating clockwise -> changes west to north"
+
+[fa0c40f5-6ba3-443d-a4b3-58cbd6cb8d63]
+description = "Rotating counter-clockwise -> changes north to west"
+
+[da33d734-831f-445c-9907-d66d7d2a92e2]
+description = "Rotating counter-clockwise -> changes west to south"
+
+[bd1ca4b9-4548-45f4-b32e-900fc7c19389]
+description = "Rotating counter-clockwise -> changes south to east"
+
+[2de27b67-a25c-4b59-9883-bc03b1b55bba]
+description = "Rotating counter-clockwise -> changes east to north"
+
+[f0dc2388-cddc-4f83-9bed-bcf46b8fc7b8]
+description = "Moving forward one -> facing north increments Y"
+
+[2786cf80-5bbf-44b0-9503-a89a9c5789da]
+description = "Moving forward one -> facing south decrements Y"
+
+[84bf3c8c-241f-434d-883d-69817dbd6a48]
+description = "Moving forward one -> facing east increments X"
+
+[bb69c4a7-3bbf-4f64-b415-666fa72d7b04]
+description = "Moving forward one -> facing west decrements X"
+
+[e34ac672-4ed4-4be3-a0b8-d9af259cbaa1]
+description = "Follow series of instructions -> moving east and north from README"
+
+[f30e4955-4b47-4aa3-8b39-ae98cfbd515b]
+description = "Follow series of instructions -> moving west and north"
+
+[3e466bf6-20ab-4d79-8b51-264165182fca]
+description = "Follow series of instructions -> moving west and south"
+
+[41f0bb96-c617-4e6b-acff-a4b279d44514]
+description = "Follow series of instructions -> moving east and north"

exercises/practice/robot-simulator/robot-simulator-test.rkt

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+#lang racket/base
+
+(require racket/class)
+(require "robot-simulator.rkt")
+
+(module+ test
+  (require rackunit rackunit/text-ui))
+
+(module+ test
+  (define suite
+    (test-suite "robot simulator tests"
+      (test-case "at origin facing north"
+        (define robot (new robot% [position '(0 0)] [direction 'north]))
+        (check-equal? (get-field position robot) '(0 0))
+        (check-equal? (get-field direction robot) 'north))
+
+      (test-case "at negative position facing south"
+        (define robot (new robot% [position '(-1 -1)] [direction 'south]))
+        (check-equal? (get-field position robot) '(-1 -1))
+        (check-equal? (get-field direction robot) 'south))
+
+      (test-case "changes north to east"
+        (define robot (new robot% [position '(0 0)] [direction 'north]))
+	(send robot move "R")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'east))
+
+      (test-case "changes east to south"
+        (define robot (new robot% [position '(0 0)] [direction 'east]))
+        (send robot move "R")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'south))
+
+      (test-case "changes south to west"
+        (define robot (new robot% [position '(0 0)] [direction 'south]))
+        (send robot move "R")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'west))
+
+      (test-case "changes west to north"
+        (define robot (new robot% [position '(0 0)] [direction 'west]))
+        (send robot move "R")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'north))
+
+      (test-case "changes north to west"
+        (define robot (new robot% [position '(0 0)] [direction 'north]))
+        (send robot move "L")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'west))
+
+      (test-case "changes west to south"
+        (define robot (new robot% [position '(0 0)] [direction 'west]))
+        (send robot move "L")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'south))
+
+      (test-case "changes south to east"
+        (define robot (new robot% [position '(0 0)] [direction 'south]))
+        (send robot move "L")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'east))
+
+      (test-case "changes east to north"
+        (define robot (new robot% [position '(0 0)] [direction 'east]))
+        (send robot move "L")
+	(check-equal? (get-field position robot) '(0 0))
+	(check-equal? (get-field direction robot) 'north))
+
+      (test-case "facing north increments Y"
+        (define robot (new robot% [position '(0 0)] [direction 'north]))
+        (send robot move "A")
+	(check-equal? (get-field position robot) '(0 1))
+	(check-equal? (get-field direction robot) 'north))
+
+      (test-case "facing south decrements Y"
+        (define robot (new robot% [position '(0 0)] [direction 'south]))
+          (send robot move "A")
+	(check-equal? (get-field position robot) '(0 -1))
+	(check-equal? (get-field direction robot) 'south))
+
+      (test-case "facing east increments X"
+        (define robot (new robot% [position '(0 0)] [direction 'east]))
+          (send robot move "A")
+	(check-equal? (get-field position robot) '(1 0))
+	(check-equal? (get-field direction robot) 'east))
+
+      (test-case "facing west decrements X"
+        (define robot (new robot% [position '(0 0)] [direction 'west]))
+        (send robot move "A")
+	(check-equal? (get-field position robot) '(-1 0))
+	(check-equal? (get-field direction robot) 'west))
+
+      (test-case "moving east and north from README"
+        (define robot (new robot% [position '(7 3)] [direction 'north]))
+        (send robot move "RAALAL")
+	(check-equal? (get-field position robot) '(9 4))
+	(check-equal? (get-field direction robot) 'west))
+
+      (test-case "moving west and north"
+        (define robot (new robot% [position '(0 0)] [direction 'north]))
+          (send robot move "LAAARALA")
+	(check-equal? (get-field position robot) '(-4 1))
+	(check-equal? (get-field direction robot) 'west))
+
+      (test-case "moving west and south"
+        (define robot (new robot% [position '(2 -7)] [direction 'east]))
+        (send robot move "RRAAAAALA")
+	(check-equal? (get-field position robot) '(-3 -8))
+	(check-equal? (get-field direction robot) 'south))
+
+      (test-case "moving east and north"
+        (define robot (new robot% [position '(8 4)] [direction 'south]))
+        (send robot move "LAAARRRALLLL")
+	(check-equal? (get-field position robot) '(11 5))
+	(check-equal? (get-field direction robot) 'north))))
+
+  (run-tests suite))

exercises/practice/robot-simulator/robot-simulator.rkt

@@ -0,0 +1,7 @@
+#lang racket
+
+(provide robot%)
+
+(define robot%
+  (class object%
+    (error "Not implemented yet")))