Add "D&D Character" practice exercise (#2753)

config.json

@@ -753,6 +753,18 @@
           "math"
         ]
       },
+      {
+        "slug": "dnd-character",
+        "name": "D&D Character",
+        "uuid": "fb42541e-6334-495f-b63b-e3c3d4ac1ed6",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3,
+        "topics": [
+          "structs",
+          "randomness"
+        ]
+      },
       {
         "slug": "etl",
         "name": "ETL",

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 +1,21 @@
+{
+  "authors": ["jesse-kroon"],
+  "contributors": ["andrerfcsantos"],
+  "files": {
+    "solution": [
+      "dnd_character.go"
+    ],
+    "test": [
+      "dnd_character_test.go"
+    ],
+    "editor": [
+      "cases_test.go"
+    ],
+    "example": [
+      ".meta/example.go"
+    ]
+  },
+  "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.go

@@ -0,0 +1,56 @@
+package dndcharacter
+
+import (
+	"math"
+	"math/rand"
+	"slices"
+)
+
+type Character struct {
+	Strength     int
+	Dexterity    int
+	Constitution int
+	Intelligence int
+	Wisdom       int
+	Charisma     int
+	Hitpoints    int
+}
+
+// Modifier calculates the ability modifier for a given ability score
+func Modifier(score int) int {
+	return int(math.Floor(float64(score-10) / 2.0))
+}
+
+// Ability uses randomness to generate the score for an ability
+func Ability() int {
+	var scores []int
+	var sum int
+
+	for i := 0; i < 4; i++ {
+		roll := RollDice()
+		sum += roll
+		scores = append(scores, roll)
+	}
+
+	return sum - slices.Min(scores)
+}
+
+// GenerateCharacter creates a new Character with random scores for abilities
+func GenerateCharacter() Character {
+	character := Character{
+		Strength:     Ability(),
+		Dexterity:    Ability(),
+		Constitution: Ability(),
+		Intelligence: Ability(),
+		Wisdom:       Ability(),
+		Charisma:     Ability(),
+	}
+
+	character.Hitpoints = 10 + Modifier(character.Constitution)
+
+	return character
+}
+
+func RollDice() int {
+	return rand.Intn(6) + 1
+}

exercises/practice/dnd-character/.meta/gen.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"log"
+	"text/template"
+
+	"../../../../gen"
+)
+
+func main() {
+	t, err := template.New("").Parse(tmpl)
+	if err != nil {
+		log.Fatal(err)
+	}
+	var j = map[string]interface{}{
+		"modifier":  &[]modifierTestCase{},
+		"ability":   &[]emptyTestCase{},
+		"character": &[]emptyTestCase{},
+	}
+	if err := gen.Gen("dnd-character", j, t); err != nil {
+		log.Fatal(err)
+	}
+}
+
+// Problem specifications have the 'ability' and 'character' properties,
+// and the test generator expects them to be present.
+// However, for these properties, generating test cases automatically
+// from the 'input' and the 'expected' objects is not trivial.
+// To satisfy the test generator, we create an emptyTestCase for these properties
+// and implement the tests manually.
+// In the future we might adapt the test generator to also cover this exercise.
+type emptyTestCase struct{}
+
+type modifierTestInput struct {
+	Score int `json:"score"`
+}
+
+type modifierTestCase struct {
+	Description string            `json:"description"`
+	Input       modifierTestInput `json:"input"`
+	Expected    int               `json:"expected"`
+}
+
+var tmpl = `
+package dndcharacter
+
+{{.Header}}
+
+type modifierTestInput struct {
+	Score int
+}
+
+var modifierTests = []struct {
+	description    string
+	input          modifierTestInput
+	expected       int
+}{
+	{{range .J.modifier}} 
+		{
+			description: {{printf "%q"  .Description}},
+			input: modifierTestInput { 
+				Score: {{printf "%d" .Input.Score}},
+			},
+			expected: {{printf "%d"  .Expected}},
+		},
+	{{end}}
+}
+`

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

@@ -0,0 +1,72 @@
+# 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"
+include = false
+
+[dca2b2ec-f729-4551-84b9-078876bb4808]
+description = "each ability is only calculated once"
+reimplements = "2ca77b9b-c099-46c3-a02c-0d0f68ffa0fe"