Add robot-name exercise

config.json

@@ -765,6 +765,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "robot-name",
+        "name": "Robot Name",
+        "uuid": "54eb5f14-2b7c-4201-b38d-a25ce2cdae97",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
       }
     ],
     "foregone": [

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

@@ -0,0 +1,8 @@
+# Hints
+
+## General
+
+- Use the [setarg] predicate to mutate data.
+- The [setarg] predicate uses **1-based indexing**, so the first element is at index 1.
+
+[setarg]: https://www.swi-prolog.org/pldoc/doc_for?object=setarg/3

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

@@ -0,0 +1,9 @@
+# Instructions append
+
+## Mutable data in Prolog
+
+By default, values in Prolog are _immutable_, which means that values never change (you'll have to introduce a new variable for each new value).
+While this is great for the vast majority of use cases, this exercise _does_ require mutating values.
+To mutate data in Prolog, you can use the [setarg] predicate.
+
+[setarg]: https://www.swi-prolog.org/pldoc/doc_for?object=setarg/3

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/config.json

@@ -0,0 +1,18 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "robot_name.pl"
+    ],
+    "test": [
+      "robot_name_tests.plt"
+    ],
+    "example": [
+      ".meta/robot_name.example.pl"
+    ]
+  },
+  "blurb": "Manage robot factory settings.",
+  "source": "A debugging session with Paul Blackwell at gSchool."
+}

exercises/practice/robot-name/.meta/robot_name.example.pl

@@ -0,0 +1,19 @@
+letters(Letters) :- string_chars("ABCDEFGHIJKLMNOPQRSTUVWXZY", Letters).
+digits(Digits) :- string_chars("0123456789", Digits).
+
+generate_name(Name) :-
+    letters(Letters),
+    digits(Digits),
+    random_member(L1, Letters), random_member(L2, Letters),
+    random_member(D1, Digits), random_member(D2, Digits), random_member(D3, Digits),
+    string_chars(Name, [L1,L2,D1,D2,D3]).
+
+create_robot(Robot) :-
+    generate_name(Name),
+    Robot = robot(Name).
+
+robot_name(robot(Name), Name).
+
+reset_name(Robot) :-
+    generate_name(Name),
+    setarg(1, Robot, Name).

exercises/practice/robot-name/robot_name.pl

@@ -0,0 +1,3 @@
+create_robot(Robot).
+robot_name(Robot, Name).
+reset_name(Robot).

exercises/practice/robot-name/robot_name_tests.plt

@@ -0,0 +1,41 @@
+pending :-
+    current_prolog_flag(argv, ['--all'|_]).
+pending :-
+    write('\nA TEST IS PENDING!\n'),
+    fail.
+
+:- begin_tests(robot_name).
+
+    test(has_name, condition(true)) :-
+        create_robot(Robot),
+        robot_name(Robot, Name),
+        string_concat(Letters, Digits, Name),
+        string_length(Letters, 2),
+        string_length(Digits, 3),
+        string_chars(Letters, LettersChars),
+        string_chars(Digits, DigitsChars),
+        maplist([C]>>char_type(C, upper), LettersChars),
+        maplist([C]>>char_type(C, digit), DigitsChars),
+        !.
+
+    test(name_sticks, condition(pending)) :-
+        create_robot(Robot),
+        robot_name(Robot, Name1),
+        robot_name(Robot, Name2),
+        Name1 == Name2.
+
+    test(different_robots_have_different_names, condition(pending)) :-
+        create_robot(Robot1),
+        create_robot(Robot2),
+        robot_name(Robot1, Name1),
+        robot_name(Robot2, Name2),
+        Name1 \== Name2.
+
+    test(reset_name, condition(pending)) :-
+        create_robot(Robot),
+        robot_name(Robot, Name1),
+        reset_name(Robot),
+        robot_name(Robot, Name2),
+        Name1 \== Name2.
+
+:- end_tests(robot_name).