Add practice exercise: diamond (#197)

Author: jimmytty

config.json

@@ -346,6 +346,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "diamond",
+        "name": "Diamond",
+        "uuid": "8f223ea0-4bd2-4e40-99ac-d5d13d9726e5",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "hamming",
         "name": "Hamming",

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": [
+    "jimmytty"
+  ],
+  "files": {
+    "solution": [
+      "diamond.sql"
+    ],
+    "test": [
+      "diamond_test.sql"
+    ],
+    "example": [
+      ".meta/example.sql"
+    ]
+  },
+  "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/example.sql

@@ -0,0 +1,37 @@
+UPDATE diamond
+   SET result = (
+         WITH
+           lengths (len, chr) AS (
+             SELECT (ROW_NUMBER() OVER () - 1) * 2,
+                    CHAR(value)
+               FROM GENERATE_SERIES(UNICODE('A'), UNICODE(letter))
+           ),
+           lines (line) AS (
+             SELECT IIF(chr = 'A', chr, PRINTF('%-*c%c', len, chr, chr))
+               FROM lengths
+           ),
+           padding (rn, line) AS (
+             SELECT ROW_NUMBER() OVER (),
+                    PRINTF('%*s%s%-*s', pad, '', line, pad, '')
+               FROM (
+                 SELECT line,
+                        (SELECT MAX(LENGTH(line)) FROM lines) len,
+                        ((SELECT MAX(LENGTH(line)) FROM lines) - LENGTH(line))
+                          / 2 pad
+                   FROM lines
+               )
+           ),
+           top (line) AS (SELECT line FROM padding ORDER BY rn ASC),
+           bottom (line) AS (
+             SELECT line
+               FROM padding
+              WHERE rn < (SELECT MAX(rn) FROM padding) ORDER BY rn DESC
+           )
+         SELECT GROUP_CONCAT(line, CHAR(10))
+           FROM (
+             SELECT line FROM top
+              UNION ALL
+             SELECT line FROM bottom
+           )
+       )
+;

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/create_fixture.sql

@@ -0,0 +1,10 @@
+DROP TABLE IF EXISTS diamond;
+CREATE TABLE diamond (
+  letter TEXT NOT NULL,
+  result TEXT
+);
+
+.mode csv
+.import ./data.csv diamond
+
+UPDATE diamond SET result = NULL;

exercises/practice/diamond/create_test_table.sql

@@ -0,0 +1,25 @@
+DROP TABLE IF EXISTS tests;
+CREATE TABLE IF NOT EXISTS tests (
+  -- uuid and description are taken from the test.toml file
+  uuid TEXT PRIMARY KEY,
+  description TEXT NOT NULL,
+  -- The following section is needed by the online test-runner
+  status TEXT DEFAULT 'fail',
+  message TEXT,
+  output TEXT,
+  test_code TEXT,
+  task_id INTEGER DEFAULT NULL,
+  -- Here are columns for the actual tests
+  letter TEXT NOT NULL,
+  expected TEXT NOT NULL
+);
+
+INSERT INTO tests (uuid, description, letter, expected)
+VALUES
+('202fb4cc-6a38-4883-9193-a29d5cb92076', 'Degenerate case with a single ''A'' row', 'A', 'A'),
+('bd6a6d78-9302-42e9-8f60-ac1461e9abae', 'Degenerate case with no row containing 3 distinct groups of spaces', 'B', ' A \nB B\n A '),
+('af8efb49-14ed-447f-8944-4cc59ce3fd76', 'Smallest non-degenerate case with odd diamond side length', 'C', '  A  \n B B \nC   C\n B B \n  A  '),
+('e0c19a95-9888-4d05-86a0-fa81b9e70d1d', 'Smallest non-degenerate case with even diamond side length', 'D', '   A   \n  B B  \n C   C \nD     D\n C   C \n  B B  \n   A   '),
+('82ea9aa9-4c0e-442a-b07e-40204e925944', 'Largest possible diamond', 'Z', '                         A                         \n                        B B                        \n                       C   C                       \n                      D     D                      \n                     E       E                     \n                    F         F                    \n                   G           G                   \n                  H             H                  \n                 I               I                 \n                J                 J                \n               K                   K               \n              L                     L              \n             M                       M             \n            N                         N            \n           O                           O           \n          P                             P          \n         Q                               Q         \n        R                                 R        \n       S                                   S       \n      T                                     T      \n     U                                       U     \n    V                                         V    \n   W                                           W   \n  X                                             X  \n Y                                               Y \nZ                                                 Z\n Y                                               Y \n  X                                             X  \n   W                                           W   \n    V                                         V    \n     U                                       U     \n      T                                     T      \n       S                                   S       \n        R                                 R        \n         Q                               Q         \n          P                             P          \n           O                           O           \n            N                         N            \n             M                       M             \n              L                     L              \n               K                   K               \n                J                 J                \n                 I               I                 \n                  H             H                  \n                   G           G                   \n                    F         F                    \n                     E       E                     \n                      D     D                      \n                       C   C                       \n                        B B                        \n                         A                         ');
+
+UPDATE tests SET expected = REPLACE(expected, '\n', CHAR(10));

exercises/practice/diamond/data.csv

@@ -0,0 +1,5 @@
+"A",
+"B",
+"C",
+"D",
+"Z",

exercises/practice/diamond/diamond.sql

@@ -0,0 +1,7 @@
+-- Schema:
+-- CREATE TABLE diamond (
+--   letter TEXT NOT NULL,
+--   result TEXT
+-- );
+--
+-- Task: update the diamond table and set result column based on the letter.

exercises/practice/diamond/diamond_test.sql

@@ -0,0 +1,36 @@
+-- Create database:
+.read ./create_fixture.sql
+
+-- Read user student solution and save any output as markdown in user_output.md:
+.mode markdown
+.output user_output.md
+.read ./diamond.sql
+.output
+
+-- Create a clean testing environment:
+.read ./create_test_table.sql
+
+-- Comparison of user input and the tests updates the status for each test:
+UPDATE tests
+   SET status = 'pass'
+  FROM (SELECT letter, result FROM diamond) AS actual
+ WHERE (actual.letter, actual.result) = (tests.letter, tests.expected);
+
+-- Update message for failed tests to give helpful information:
+UPDATE tests
+   SET message = (
+         'Result for "' || tests.letter || '"' || ' is <'
+         || COALESCE(actual.result, 'NULL')
+         || '> but should be <' || tests.expected || '>'
+       )
+  FROM (SELECT letter, result FROM diamond) AS actual
+ WHERE actual.letter = tests.letter AND tests.status = 'fail';
+
+-- Save results to ./output.json (needed by the online test-runner)
+.mode json
+.once './output.json'
+SELECT description, status, message, output, test_code, task_id FROM tests;
+
+-- Display test results in readable form for the student:
+.mode table
+SELECT description, status, message FROM tests;