* add practice exercise: proverb

config.json

@@ -354,6 +354,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "proverb",
+        "name": "Proverb",
+        "uuid": "10c51241-2399-4a0c-84cf-390a000f3c3b",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "rest-api",
         "name": "REST API",

exercises/practice/proverb/.docs/instructions.append.md

@@ -0,0 +1,7 @@
+# SQLite-specific instructions
+
+## JSON documentation
+
+[JSON Functions And Operators][json-docs]
+
+[json-docs]: https://www.sqlite.org/json1.html

exercises/practice/proverb/.docs/instructions.md

@@ -0,0 +1,19 @@
+# Instructions
+
+For want of a horseshoe nail, a kingdom was lost, or so the saying goes.
+
+Given a list of inputs, generate the relevant proverb.
+For example, given the list `["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]`, you will output the full text of this proverbial rhyme:
+
+```text
+For want of a nail the shoe was lost.
+For want of a shoe the horse was lost.
+For want of a horse the rider was lost.
+For want of a rider the message was lost.
+For want of a message the battle was lost.
+For want of a battle the kingdom was lost.
+And all for the want of a nail.
+```
+
+Note that the list of inputs may vary; your solution should be able to handle lists of arbitrary length and content.
+No line of the output text should be a static, unchanging string; all should vary according to the input given.

exercises/practice/proverb/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "jimmytty"
+  ],
+  "files": {
+    "solution": [
+      "proverb.sql"
+    ],
+    "test": [
+      "proverb_test.sql"
+    ],
+    "example": [
+      ".meta/example.sql"
+    ]
+  },
+  "blurb": "For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/For_Want_of_a_Nail"
+}

exercises/practice/proverb/.meta/example.sql

@@ -0,0 +1,33 @@
+UPDATE proverb
+   SET result = ''
+ WHERE JSON(strings) = '[]'
+;
+
+UPDATE proverb
+   SET result = (
+     WITH RECURSIVE to_pieces (strings, i, len, piece) AS (
+       VALUES(strings, 0, JSON_ARRAY_LENGTH(strings) - 1, NULL)
+       UNION ALL
+       SELECT strings, i+1, len,
+              PRINTF(
+                'For want of a %s the %s was lost.',
+                JSON_EXTRACT(strings, PRINTF('$[%d]', i)),
+                JSON_EXTRACT(strings, PRINTF('$[%d]', i+1))
+              )
+         FROM to_pieces
+        WHERE i < len
+     )
+     SELECT group_concat(piece, CHAR(10))
+       FROM (
+         SELECT piece
+           FROM to_pieces
+          WHERE piece NOTNULL
+          UNION ALL
+         SELECT PRINTF(
+                  'And all for the want of a %s.',
+                  JSON_EXTRACT(strings, '$[0]')
+                )
+       )
+   )
+ WHERE result ISNULL
+;

exercises/practice/proverb/.meta/tests.toml

@@ -0,0 +1,28 @@
+# 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.
+
+[e974b73e-7851-484f-8d6d-92e07fe742fc]
+description = "zero pieces"
+
+[2fcd5f5e-8b82-4e74-b51d-df28a5e0faa4]
+description = "one piece"
+
+[d9d0a8a1-d933-46e2-aa94-eecf679f4b0e]
+description = "two pieces"
+
+[c95ef757-5e94-4f0d-a6cb-d2083f5e5a83]
+description = "three pieces"
+
+[433fb91c-35a2-4d41-aeab-4de1e82b2126]
+description = "full proverb"
+
+[c1eefa5a-e8d9-41c7-91d4-99fab6d6b9f7]
+description = "four pieces modernized"

exercises/practice/proverb/create_fixture.sql

@@ -0,0 +1,10 @@
+DROP TABLE IF EXISTS proverb;
+CREATE TABLE proverb (
+    strings TEXT NOT NULL,    -- json array containing the input words
+    result  TEXT
+);
+
+.mode csv
+.import ./data.csv proverb
+
+UPDATE proverb SET result = NULL;

exercises/practice/proverb/create_test_table.sql

@@ -0,0 +1,26 @@
+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
+    strings TEXT NOT NULL,    -- json array
+    expected TEXT NOT NULL
+);
+
+INSERT INTO tests (uuid, description, strings, expected)
+    VALUES
+        ('e974b73e-7851-484f-8d6d-92e07fe742fc', 'zero pieces', '[]', ''),
+        ('2fcd5f5e-8b82-4e74-b51d-df28a5e0faa4', 'one piece', '["nail"]', 'And all for the want of a nail.'),
+        ('d9d0a8a1-d933-46e2-aa94-eecf679f4b0e', 'two pieces', '["nail","shoe"]', 'For want of a nail the shoe was lost.\nAnd all for the want of a nail.'),
+        ('c95ef757-5e94-4f0d-a6cb-d2083f5e5a83', 'three pieces', '["nail","shoe","horse"]', 'For want of a nail the shoe was lost.\nFor want of a shoe the horse was lost.\nAnd all for the want of a nail.'),
+        ('433fb91c-35a2-4d41-aeab-4de1e82b2126', 'full proverb', '["nail","shoe","horse","rider","message","battle","kingdom"]', 'For want of a nail the shoe was lost.\nFor want of a shoe the horse was lost.\nFor want of a horse the rider was lost.\nFor want of a rider the message was lost.\nFor want of a message the battle was lost.\nFor want of a battle the kingdom was lost.\nAnd all for the want of a nail.'),
+        ('c1eefa5a-e8d9-41c7-91d4-99fab6d6b9f7', 'four pieces modernized', '["pin","gun","soldier","battle"]', 'For want of a pin the gun was lost.\nFor want of a gun the soldier was lost.\nFor want of a soldier the battle was lost.\nAnd all for the want of a pin.');
+
+UPDATE tests SET expected = REPLACE(expected, '\n', CHAR(10));

exercises/practice/proverb/data.csv

@@ -0,0 +1,6 @@
+"[]",
+"[""nail""]",
+"[""nail"",""shoe""]",
+"[""nail"",""shoe"",""horse""]",
+"[""nail"",""shoe"",""horse"",""rider"",""message"",""battle"",""kingdom""]",
+"[""pin"",""gun"",""soldier"",""battle""]",

exercises/practice/proverb/proverb.sql

@@ -0,0 +1,7 @@
+-- Schema:
+-- CREATE TABLE proverb (
+--     strings TEXT NOT NULL,    -- json array  containing the input words
+--     result  TEXT
+-- );
+--
+-- Task: update proverb table and set result column based on the strings.

exercises/practice/proverb/proverb_test.sql

@@ -0,0 +1,40 @@
+-- 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 ./proverb.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 strings, result FROM proverb) AS actual
+WHERE (actual.strings, actual.result) = (tests.strings, tests.expected);
+
+-- Update message for failed tests to give helpful information:
+UPDATE tests
+SET message = (
+    'Result for "'
+    || tests.strings
+    || '"'
+    || ' is <' || COALESCE(actual.result, 'NULL')
+    || '> but should be <' || tests.expected || '>'
+)
+FROM (SELECT strings, result FROM proverb) AS actual
+WHERE actual.strings = tests.strings 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;