Add robot simulator (#393)

config.json

@@ -308,6 +308,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "robot-simulator",
+        "name": "Robot Simulator",
+        "uuid": "575a40bd-2ff9-4623-ae98-c8d9b9f279a8",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "rna-transcription",
         "name": "RNA Transcription",

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 +1,18 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "robot-simulator.el"
+    ],
+    "test": [
+      "robot-simulator-test.el"
+    ],
+    "example": [
+      ".meta/example.el"
+    ]
+  },
+  "blurb": "Write a robot simulator.",
+  "source": "Inspired by an interview question at a famous company."
+}

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

@@ -0,0 +1,48 @@
+;;; robot-simulator.el --- robot-simulator Exercise (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defconst directions [north east south west])
+
+
+(defconst steps '((north  . (0 1))
+                  (east   . (1 0))
+                  (south  . (0 -1))
+                  (west   . (-1 0))))
+
+
+(defun create-robot (x y direction)
+  (record 'robot x y direction))
+
+
+(defun move (robot instructions)
+  (let ((state robot))
+    (seq-doseq (instruction instructions)
+      (cond ((equal ?L instruction)
+             (rotate state -1))
+            ((equal ?R instruction)
+             (rotate state 1))
+            ((equal ?A instruction)
+             (advance state))))
+    state))
+
+
+(defun rotate (robot offset)
+  (let* ((old-index (cl-position (aref robot 3) directions))
+         (new-index (mod (+ old-index offset) 4)))
+    (aset robot 3 (aref directions new-index))))
+
+
+(defun advance (robot)
+  (let* ((delta (assq (aref robot 3) steps))
+         (delta-x (cadr delta))
+         (delta-y (caddr delta)))
+    (aset robot 1 (+ delta-x (aref robot 1)))
+    (aset robot 2 (+ delta-y (aref robot 2)))))
+
+
+(provide 'robot-simulator)
+;;; robot-simulator.el ends here

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.el

@@ -0,0 +1,104 @@
+;;; robot-simulator-test.el --- Tests for robot-simulator (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(load-file "robot-simulator.el")
+(declare-function create-robot "robot-simulator.el" (x y direction))
+(declare-function move "robot-simulator.el" (robot instructions))
+
+
+(ert-deftest create-robot-at-origin-facing-north ()
+    (should (equal #s(robot 0 0 north)
+                   (create-robot 0 0 'north))))
+
+
+(ert-deftest create-robot-at-negative-position-facing-south ()
+    (should (equal #s(robot -1 -1 south)
+                   (create-robot -1 -1 'south))))
+
+
+(ert-deftest rotating-clockwise-changes-north-to-east ()
+    (should (equal #s(robot 0 0 east)
+                   (move (create-robot 0 0 'north) "R"))))
+
+
+(ert-deftest rotating-clockwise-changes-east-to-south ()
+    (should (equal #s(robot 0 0 south)
+                   (move (create-robot 0 0 'east) "R"))))
+
+
+(ert-deftest rotating-clockwise-changes-south-to-west ()
+    (should (equal #s(robot 0 0 west)
+                   (move (create-robot 0 0 'south) "R"))))
+
+
+(ert-deftest rotating-clockwise-changes-west-to-north ()
+    (should (equal #s(robot 0 0 north)
+                   (move (create-robot 0 0 'west) "R"))))
+
+
+(ert-deftest rotating-counter-clockwise-changes-north-to-west ()
+    (should (equal #s(robot 0 0 west)
+                   (move (create-robot 0 0 'north) "L"))))
+
+
+(ert-deftest rotating-counter-clockwise-changes-west-to-south ()
+    (should (equal #s(robot 0 0 south)
+                   (move (create-robot 0 0 'west) "L"))))
+
+
+(ert-deftest rotating-counter-clockwise-changes-south-to-east ()
+    (should (equal #s(robot 0 0 east)
+                   (move (create-robot 0 0 'south) "L"))))
+
+
+(ert-deftest rotating-counter-clockwise-changes-east-to-north ()
+    (should (equal #s(robot 0 0 north)
+                   (move (create-robot 0 0 'east) "L"))))
+
+
+(ert-deftest moving-forward-one-facing-north-increments-y ()
+    (should (equal #s(robot 0 1 north)
+                   (move (create-robot 0 0 'north) "A"))))
+
+
+(ert-deftest moving-forward-one-facing-south-decrements-y ()
+    (should (equal #s(robot 0 -1 south)
+                   (move (create-robot 0 0 'south) "A"))))
+
+
+(ert-deftest moving-forward-one-facing-east-increments-x ()
+    (should (equal #s(robot 1 0 east)
+                   (move (create-robot 0 0 'east) "A"))))
+
+
+(ert-deftest moving-forward-one-facing-west-decrements-x ()
+    (should (equal #s(robot -1 0 west)
+                   (move (create-robot 0 0 'west) "A"))))
+
+
+(ert-deftest follow-series-of-instructions-moving-east-and-north-from-README ()
+    (should (equal #s(robot 9 4 west)
+                   (move (create-robot 7 3 'north) "RAALAL"))))
+
+
+(ert-deftest follow-series-of-instructions-moving-west-and-north ()
+    (should (equal #s(robot -4 1 west)
+                   (move (create-robot 0 0 'north) "LAAARALA"))))
+
+
+(ert-deftest follow-series-of-instructions-moving-west-and-south ()
+    (should (equal #s(robot -3 -8 south)
+                   (move (create-robot 2 -7 'east) "RRAAAAALA"))))
+
+
+(ert-deftest follow-series-of-instructions-moving-east-and-north ()
+    (should (equal #s(robot 11 5 north)
+                   (move (create-robot 8 4 'south) "LAAARRRALLLL"))))
+
+
+(provide 'robot-simulator-test)
+;;; robot-simulator-test.el ends here

exercises/practice/robot-simulator/robot-simulator.el

@@ -0,0 +1,17 @@
+;;; robot-simulator.el --- robot-simulator (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defun create-robot (x y direction)
+ (error "Delete this S-Expression and write your own implementation"))
+
+
+(defun move (robot instructions)
+ (error "Delete this S-Expression and write your own implementation"))
+
+
+(provide 'robot-simulator)
+;;; robot-simulator.el ends here