Add dnd-character (#295)

config.json

@@ -81,6 +81,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "dnd-character",
+        "name": "D&D Character",
+        "uuid": "6402b034-ab93-44f6-9f74-1547924449de",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "perfect-numbers",
         "name": "Perfect Numbers",

exercises/practice/dnd-character/.docs/instructions.md

@@ -0,0 +1,31 @@
+# Instructions
+
+For a game of [Dungeons & Dragons][dnd], each player starts by generating a character they can play with.
+This character has, among other things, six abilities; strength, dexterity, constitution, intelligence, wisdom and charisma.
+These six abilities have scores that are determined randomly.
+You do this by rolling four 6-sided dice and record the sum of the largest three dice.
+You do this six times, once for each ability.
+
+Your character's initial hitpoints are 10 + your character's constitution modifier.
+You find your character's constitution modifier by subtracting 10 from your character's constitution, divide by 2 and round down.
+
+Write a random character generator that follows the rules above.
+
+For example, the six throws of four dice may look like:
+
+- 5, 3, 1, 6: You discard the 1 and sum 5 + 3 + 6 = 14, which you assign to strength.
+- 3, 2, 5, 3: You discard the 2 and sum 3 + 5 + 3 = 11, which you assign to dexterity.
+- 1, 1, 1, 1: You discard the 1 and sum 1 + 1 + 1 = 3, which you assign to constitution.
+- 2, 1, 6, 6: You discard the 1 and sum 2 + 6 + 6 = 14, which you assign to intelligence.
+- 3, 5, 3, 4: You discard the 3 and sum 5 + 3 + 4 = 12, which you assign to wisdom.
+- 6, 6, 6, 6: You discard the 6 and sum 6 + 6 + 6 = 18, which you assign to charisma.
+
+Because constitution is 3, the constitution modifier is -4 and the hitpoints are 6.
+
+## Notes
+
+Most programming languages feature (pseudo-)random generators, but few programming languages are designed to roll dice.
+One such language is [Troll][troll].
+
+[dnd]: https://en.wikipedia.org/wiki/Dungeons_%26_Dragons
+[troll]: https://di.ku.dk/Ansatte/?pure=da%2Fpublications%2Ftroll-a-language-for-specifying-dicerolls(84a45ff0-068b-11df-825d-000ea68e967b)%2Fexport.html

exercises/practice/dnd-character/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "dnd-character.rkt"
+    ],
+    "test": [
+      "dnd-character-test.rkt"
+    ],
+    "example": [
+      ".meta/example.rkt"
+    ]
+  },
+  "blurb": "Randomly generate Dungeons & Dragons characters.",
+  "source": "Simon Shine, Erik Schierboom",
+  "source_url": "https://github.com/exercism/problem-specifications/issues/616#issuecomment-437358945"
+}

exercises/practice/dnd-character/.meta/example.rkt

@@ -0,0 +1,34 @@
+#lang racket
+
+(provide (struct-out character)
+         ability
+         make-character
+         modifier)
+
+(struct character
+    (strength dexterity constitution intelligence wisdom charisma hitpoints))
+
+(define (ability)
+  (define (dice-rolls n)
+    (for/list ([i n])
+      (add1 (random 6))))
+  (define (drop-lowest lst)
+    (cdr (sort lst <)))
+  (define (total-score n)
+    (define dice (dice-rolls n))
+    (for/sum ([i (drop-lowest dice)])
+      i))
+  (total-score 4))
+
+(define (modifier value)
+    (floor (/ (- value 10) 2)))
+
+(define (make-character)
+    (define strength (ability))
+    (define dexterity (ability))
+    (define constitution (ability))
+    (define intelligence (ability))
+    (define wisdom (ability))
+    (define charisma (ability))
+    (define hitpoints (+ (modifier constitution) 10))
+    (character strength dexterity constitution intelligence wisdom charisma hitpoints))

exercises/practice/dnd-character/.meta/tests.toml

@@ -0,0 +1,67 @@
+# 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.
+
+[1e9ae1dc-35bd-43ba-aa08-e4b94c20fa37]
+description = "ability modifier -> ability modifier for score 3 is -4"
+
+[cc9bb24e-56b8-4e9e-989d-a0d1a29ebb9c]
+description = "ability modifier -> ability modifier for score 4 is -3"
+
+[5b519fcd-6946-41ee-91fe-34b4f9808326]
+description = "ability modifier -> ability modifier for score 5 is -3"
+
+[dc2913bd-6d7a-402e-b1e2-6d568b1cbe21]
+description = "ability modifier -> ability modifier for score 6 is -2"
+
+[099440f5-0d66-4b1a-8a10-8f3a03cc499f]
+description = "ability modifier -> ability modifier for score 7 is -2"
+
+[cfda6e5c-3489-42f0-b22b-4acb47084df0]
+description = "ability modifier -> ability modifier for score 8 is -1"
+
+[c70f0507-fa7e-4228-8463-858bfbba1754]
+description = "ability modifier -> ability modifier for score 9 is -1"
+
+[6f4e6c88-1cd9-46a0-92b8-db4a99b372f7]
+description = "ability modifier -> ability modifier for score 10 is 0"
+
+[e00d9e5c-63c8-413f-879d-cd9be9697097]
+description = "ability modifier -> ability modifier for score 11 is 0"
+
+[eea06f3c-8de0-45e7-9d9d-b8cab4179715]
+description = "ability modifier -> ability modifier for score 12 is +1"
+
+[9c51f6be-db72-4af7-92ac-b293a02c0dcd]
+description = "ability modifier -> ability modifier for score 13 is +1"
+
+[94053a5d-53b6-4efc-b669-a8b5098f7762]
+description = "ability modifier -> ability modifier for score 14 is +2"
+
+[8c33e7ca-3f9f-4820-8ab3-65f2c9e2f0e2]
+description = "ability modifier -> ability modifier for score 15 is +2"
+
+[c3ec871e-1791-44d0-b3cc-77e5fb4cd33d]
+description = "ability modifier -> ability modifier for score 16 is +3"
+
+[3d053cee-2888-4616-b9fd-602a3b1efff4]
+description = "ability modifier -> ability modifier for score 17 is +3"
+
+[bafd997a-e852-4e56-9f65-14b60261faee]
+description = "ability modifier -> ability modifier for score 18 is +4"
+
+[4f28f19c-2e47-4453-a46a-c0d365259c14]
+description = "random ability is within range"
+
+[385d7e72-864f-4e88-8279-81a7d75b04ad]
+description = "random character is valid"
+
+[2ca77b9b-c099-46c3-a02c-0d0f68ffa0fe]
+description = "each ability is only calculated once"

exercises/practice/dnd-character/dnd-character-test.rkt

@@ -0,0 +1,85 @@
+#lang racket/base
+
+(require "dnd-character.rkt")
+
+(module+ test
+  (require rackunit rackunit/text-ui)
+
+  (define character (make-character))
+  (define (in-range? n)
+    (<= 3 n 18))
+  (define (constitution->hitpoints n)
+     (+ (modifier n) 10))
+  (define (validate-character instance pred)
+    (and (pred (character-strength instance))
+         (pred (character-dexterity instance))
+         (pred (character-constitution instance))
+         (pred (character-intelligence instance))
+         (pred (character-wisdom instance))
+         (pred (character-charisma instance))
+         (eqv? (constitution->hitpoints (character-constitution instance))
+             (character-hitpoints instance))))
+
+  (define suite
+    (test-suite
+     "D&D character"
+
+     (test-eqv? "ability modifier -> ability modifier for score 3 is -4"
+                (modifier 3) -4)
+
+     (test-eqv? "ability modifier -> ability modifier for score 4 is -3"
+                (modifier 4) -3)
+
+     (test-eqv? "ability modifier -> ability modifier for score 5 is -3"
+                (modifier 5) -3)
+
+     (test-eqv? "ability modifier -> ability modifier for score 6 is -2"
+                (modifier 6) -2)
+
+     (test-eqv? "ability modifier -> ability modifier for score 7 is -2"
+                (modifier 7) -2)
+
+     (test-eqv? "ability modifier -> ability modifier for score 8 is -1"
+                (modifier 8) -1)
+
+     (test-eqv? "ability modifier -> ability modifier for score 9 is -1"
+                (modifier 9) -1)
+
+     (test-eqv? "ability modifier -> ability modifier for score 10 is 0"
+                (modifier 10) 0)
+
+     (test-eqv? "ability modifier -> ability modifier for score 11 is 0"
+                (modifier 11) 0)
+
+     (test-eqv? "ability modifier -> ability modifier for score 12 is +1"
+                (modifier 12) 1)
+
+     (test-eqv? "ability modifier -> ability modifier for score 13 is +1"
+                (modifier 13) 1)
+
+     (test-eqv? "ability modifier -> ability modifier for score 14 is +2"
+                (modifier 14) 2)
+
+     (test-eqv? "ability modifier -> ability modifier for score 15 is +2"
+                (modifier 15) 2)
+
+     (test-eqv? "ability modifier -> ability modifier for score 16 is +3"
+                (modifier 16) 3)
+
+     (test-eqv? "ability modifier -> ability modifier for score 17 is +3"
+                (modifier 17) 3)
+
+     (test-eqv? "ability modifier -> ability modifier for score 18 is +4"
+                (modifier 18) 4)
+
+     (test-true "random ability is within range"
+                (in-range? (ability)))
+
+     (test-true "random character is valid"
+                (validate-character character in-range?))
+
+     (test-eqv? "each ability is only calculated once"
+                (character-strength character)
+                (character-strength character))))
+
+  (run-tests suite))

exercises/practice/dnd-character/dnd-character.rkt

@@ -0,0 +1,18 @@
+#lang racket
+
+(provide (struct-out character)
+         ability
+         make-character
+         modifier)
+
+(struct character
+    ()) ; Add necessary struct fields
+
+(define (ability)
+  (error "Not implemented yet"))
+
+(define (modifier value)
+  (error "Not implemented yet"))
+
+(define (make-character)
+  (error "Not implemented yet"))