Add new practice exercise diamond

config.json

@@ -1310,6 +1310,20 @@
         ],
         "difficulty": 7
       },
+      {
+        "slug": "diamond",
+        "name": "Diamond",
+        "uuid": "0c2a3fce-231a-43db-98df-84fcc74c3c97",
+        "practices": [
+          "lists"
+        ],
+        "prerequisites": [
+          "strings",
+          "lists",
+          "let"
+        ],
+        "difficulty": 4
+      },
       {
         "slug": "spiral-matrix",
         "name": "Spiral Matrix",

exercises/practice/diamond/.docs/instructions.md

@@ -0,0 +1,52 @@
+# Instructions
+
+The diamond kata takes as its input a letter, and outputs it in a diamond shape.
+Given a letter, it prints a diamond starting with 'A', with the supplied letter at the widest point.
+
+## Requirements
+
+- The first row contains one 'A'.
+- The last row contains one 'A'.
+- All rows, except the first and last, have exactly two identical letters.
+- All rows have as many trailing spaces as leading spaces. (This might be 0).
+- The diamond is horizontally symmetric.
+- The diamond is vertically symmetric.
+- The diamond has a square shape (width equals height).
+- The letters form a diamond shape.
+- The top half has the letters in ascending order.
+- The bottom half has the letters in descending order.
+- The four corners (containing the spaces) are triangles.
+
+## Examples
+
+In the following examples, spaces are indicated by `·` characters.
+
+Diamond for letter 'A':
+
+```text
+A
+```
+
+Diamond for letter 'C':
+
+```text
+··A··
+·B·B·
+C···C
+·B·B·
+··A··
+```
+
+Diamond for letter 'E':
+
+```text
+····A····
+···B·B···
+··C···C··
+·D·····D·
+E·······E
+·D·····D·
+··C···C··
+···B·B···
+····A····
+```

exercises/practice/diamond/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "jiegillet"
+  ],
+  "files": {
+    "solution": [
+      "src/Diamond.elm"
+    ],
+    "test": [
+      "tests/Tests.elm"
+    ],
+    "example": [
+      ".meta/src/Diamond.example.elm"
+    ]
+  },
+  "blurb": "Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.",
+  "source": "Seb Rose",
+  "source_url": "https://web.archive.org/web/20220807163751/http://claysnow.co.uk/recycling-tests-in-tdd/"
+}

exercises/practice/diamond/.meta/src/Diamond.example.elm

@@ -0,0 +1,27 @@
+module Diamond exposing (rows)
+
+import Char
+
+
+rows : Char -> String
+rows letter =
+    let
+        side =
+            Char.toCode letter - aCode
+
+        lines =
+            List.range 0 side
+                |> List.map
+                    (\i ->
+                        String.repeat (2 * i - 1) "_"
+                            |> String.pad (2 * i + 1) (Char.fromCode (aCode + i))
+                            |> String.pad (2 * side + 1) '_'
+                    )
+    in
+    (lines ++ (lines |> List.reverse |> List.drop 1))
+        |> String.join "\n"
+
+
+aCode : Int
+aCode =
+    Char.toCode 'A'

exercises/practice/diamond/.meta/tests.toml

@@ -0,0 +1,25 @@
+# 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.
+
+[202fb4cc-6a38-4883-9193-a29d5cb92076]
+description = "Degenerate case with a single 'A' row"
+
+[bd6a6d78-9302-42e9-8f60-ac1461e9abae]
+description = "Degenerate case with no row containing 3 distinct groups of spaces"
+
+[af8efb49-14ed-447f-8944-4cc59ce3fd76]
+description = "Smallest non-degenerate case with odd diamond side length"
+
+[e0c19a95-9888-4d05-86a0-fa81b9e70d1d]
+description = "Smallest non-degenerate case with even diamond side length"
+
+[82ea9aa9-4c0e-442a-b07e-40204e925944]
+description = "Largest possible diamond"

exercises/practice/diamond/elm.json

@@ -0,0 +1,29 @@
+{
+    "type": "application",
+    "source-directories": [
+        "src"
+    ],
+    "elm-version": "0.19.1",
+    "dependencies": {
+        "direct": {
+            "elm/core": "1.0.5",
+            "elm/json": "1.1.3",
+            "elm/parser": "1.1.0",
+            "elm/random": "1.0.0",
+            "elm/regex": "1.0.0",
+            "elm/time": "1.0.0"
+        },
+        "indirect": {}
+    },
+    "test-dependencies": {
+        "direct": {
+            "elm-explorations/test": "2.1.0",
+            "rtfeldman/elm-iso8601-date-strings": "1.1.4"
+        },
+        "indirect": {
+            "elm/bytes": "1.0.8",
+            "elm/html": "1.0.0",
+            "elm/virtual-dom": "1.0.3"
+        }
+    }
+}

exercises/practice/diamond/src/Diamond.elm

@@ -0,0 +1,6 @@
+module Diamond exposing (rows)
+
+
+rows : Char -> String
+rows letter =
+    Debug.todo "Please implement rows"

exercises/practice/diamond/tests/Tests.elm

@@ -0,0 +1,98 @@
+module Tests exposing (tests)
+
+import Diamond
+import Expect
+import Test exposing (Test, describe, skip, test)
+
+
+tests : Test
+tests =
+    describe "Diamond"
+        [ -- skip <|
+          test "Degenerate case with a single 'A' row" <|
+            \() ->
+                Diamond.rows 'A'
+                    |> Expect.equal "A"
+        , skip <|
+            test "Degenerate case with no row containing 3 distinct groups of spaces" <|
+                \() ->
+                    Diamond.rows 'B'
+                        |> Expect.equal """_A_
+B_B
+_A_"""
+        , skip <|
+            test "Smallest non-degenerate case with odd diamond side length" <|
+                \() ->
+                    Diamond.rows 'C'
+                        |> Expect.equal """__A__
+_B_B_
+C___C
+_B_B_
+__A__"""
+        , skip <|
+            test "Smallest non-degenerate case with even diamond side length" <|
+                \() ->
+                    Diamond.rows 'D'
+                        |> Expect.equal """___A___
+__B_B__
+_C___C_
+D_____D
+_C___C_
+__B_B__
+___A___"""
+        , skip <|
+            test "Largest possible diamond" <|
+                \() ->
+                    Diamond.rows 'Z'
+                        |> Expect.equal """_________________________A_________________________
+________________________B_B________________________
+_______________________C___C_______________________
+______________________D_____D______________________
+_____________________E_______E_____________________
+____________________F_________F____________________
+___________________G___________G___________________
+__________________H_____________H__________________
+_________________I_______________I_________________
+________________J_________________J________________
+_______________K___________________K_______________
+______________L_____________________L______________
+_____________M_______________________M_____________
+____________N_________________________N____________
+___________O___________________________O___________
+__________P_____________________________P__________
+_________Q_______________________________Q_________
+________R_________________________________R________
+_______S___________________________________S_______
+______T_____________________________________T______
+_____U_______________________________________U_____
+____V_________________________________________V____
+___W___________________________________________W___
+__X_____________________________________________X__
+_Y_______________________________________________Y_
+Z_________________________________________________Z
+_Y_______________________________________________Y_
+__X_____________________________________________X__
+___W___________________________________________W___
+____V_________________________________________V____
+_____U_______________________________________U_____
+______T_____________________________________T______
+_______S___________________________________S_______
+________R_________________________________R________
+_________Q_______________________________Q_________
+__________P_____________________________P__________
+___________O___________________________O___________
+____________N_________________________N____________
+_____________M_______________________M_____________
+______________L_____________________L______________
+_______________K___________________K_______________
+________________J_________________J________________
+_________________I_______________I_________________
+__________________H_____________H__________________
+___________________G___________G___________________
+____________________F_________F____________________
+_____________________E_______E_____________________
+______________________D_____D______________________
+_______________________C___C_______________________
+________________________B_B________________________
+_________________________A_________________________"""
+        ]