* add new practice exercise: triangle

config.json

@@ -146,6 +146,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "triangle",
+        "name": "Triangle",
+        "uuid": "415ddeb8-cadd-42c2-b9b5-b083ecca9961",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "allergies",
         "name": "Allergies",

exercises/practice/triangle/.docs/instructions.md

@@ -0,0 +1,29 @@
+# Instructions
+
+Determine if a triangle is equilateral, isosceles, or scalene.
+
+An _equilateral_ triangle has all three sides the same length.
+
+An _isosceles_ triangle has at least two sides the same length.
+(It is sometimes specified as having exactly two sides the same length, but for the purposes of this exercise we'll say at least two.)
+
+A _scalene_ triangle has all sides of different lengths.
+
+## Note
+
+For a shape to be a triangle at all, all sides have to be of length > 0, and the sum of the lengths of any two sides must be greater than or equal to the length of the third side.
+
+In equations:
+
+Let `a`, `b`, and `c` be sides of the triangle.
+Then all three of the following expressions must be true:
+
+```text
+a + b ≥ c
+b + c ≥ a
+a + c ≥ b
+```
+
+See [Triangle Inequality][triangle-inequality]
+
+[triangle-inequality]: https://en.wikipedia.org/wiki/Triangle_inequality

exercises/practice/triangle/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "jimmytty"
+  ],
+  "files": {
+    "solution": [
+      "triangle.sql"
+    ],
+    "test": [
+      "triangle_test.sql"
+    ],
+    "example": [
+      ".meta/example.sql"
+    ]
+  },
+  "blurb": "Determine if a triangle is equilateral, isosceles, or scalene.",
+  "source": "The Ruby Koans triangle project, parts 1 & 2",
+  "source_url": "https://web.archive.org/web/20220831105330/http://rubykoans.com"
+}

exercises/practice/triangle/.meta/example.sql

@@ -0,0 +1,25 @@
+UPDATE triangle
+   SET result = FALSE
+ WHERE 0 IN (side_a, side_b, side_c)
+    OR side_a + side_b < side_c
+    OR side_b + side_c < side_a
+    OR side_a + side_c < side_b
+;
+
+UPDATE triangle
+   SET result = (side_a = side_b AND side_a = side_c)
+ WHERE property = 'equilateral'
+   AND result ISNULL
+;
+
+UPDATE triangle
+   SET result = (side_a = side_b OR side_a = side_c OR side_b = side_c)
+ WHERE property = 'isosceles'
+   AND result ISNULL
+;
+
+UPDATE triangle
+   SET result = (side_a != side_b AND side_a != side_c AND side_b != side_c)
+ WHERE property = 'scalene'
+   AND result ISNULL
+;

exercises/practice/triangle/.meta/tests.toml

@@ -0,0 +1,73 @@
+# 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.
+
+[8b2c43ac-7257-43f9-b552-7631a91988af]
+description = "equilateral triangle -> all sides are equal"
+
+[33eb6f87-0498-4ccf-9573-7f8c3ce92b7b]
+description = "equilateral triangle -> any side is unequal"
+
+[c6585b7d-a8c0-4ad8-8a34-e21d36f7ad87]
+description = "equilateral triangle -> no sides are equal"
+
+[16e8ceb0-eadb-46d1-b892-c50327479251]
+description = "equilateral triangle -> all zero sides is not a triangle"
+
+[3022f537-b8e5-4cc1-8f12-fd775827a00c]
+description = "equilateral triangle -> sides may be floats"
+
+[cbc612dc-d75a-4c1c-87fc-e2d5edd70b71]
+description = "isosceles triangle -> last two sides are equal"
+
+[e388ce93-f25e-4daf-b977-4b7ede992217]
+description = "isosceles triangle -> first two sides are equal"
+
+[d2080b79-4523-4c3f-9d42-2da6e81ab30f]
+description = "isosceles triangle -> first and last sides are equal"
+
+[8d71e185-2bd7-4841-b7e1-71689a5491d8]
+description = "isosceles triangle -> equilateral triangles are also isosceles"
+
+[840ed5f8-366f-43c5-ac69-8f05e6f10bbb]
+description = "isosceles triangle -> no sides are equal"
+
+[2eba0cfb-6c65-4c40-8146-30b608905eae]
+description = "isosceles triangle -> first triangle inequality violation"
+
+[278469cb-ac6b-41f0-81d4-66d9b828f8ac]
+description = "isosceles triangle -> second triangle inequality violation"
+
+[90efb0c7-72bb-4514-b320-3a3892e278ff]
+description = "isosceles triangle -> third triangle inequality violation"
+
+[adb4ee20-532f-43dc-8d31-e9271b7ef2bc]
+description = "isosceles triangle -> sides may be floats"
+
+[e8b5f09c-ec2e-47c1-abec-f35095733afb]
+description = "scalene triangle -> no sides are equal"
+
+[2510001f-b44d-4d18-9872-2303e7977dc1]
+description = "scalene triangle -> all sides are equal"
+
+[c6e15a92-90d9-4fb3-90a2-eef64f8d3e1e]
+description = "scalene triangle -> first and second sides are equal"
+
+[3da23a91-a166-419a-9abf-baf4868fd985]
+description = "scalene triangle -> first and third sides are equal"
+
+[b6a75d98-1fef-4c42-8e9a-9db854ba0a4d]
+description = "scalene triangle -> second and third sides are equal"
+
+[70ad5154-0033-48b7-af2c-b8d739cd9fdc]
+description = "scalene triangle -> may not violate triangle inequality"
+
+[26d9d59d-f8f1-40d3-ad58-ae4d54123d7d]
+description = "scalene triangle -> sides may be floats"

exercises/practice/triangle/create_fixture.sql

@@ -0,0 +1,13 @@
+DROP TABLE IF EXISTS triangle;
+CREATE TABLE triangle (
+    property TEXT    NOT NULL,
+    side_a   REAL    NOT NULL,
+    side_b   REAL    NOT NULL,
+    side_c   REAL    NOT NULL,
+    result   BOOLEAN
+);
+
+.mode csv
+.import ./data.csv triangle
+
+UPDATE triangle SET result = NULL;

exercises/practice/triangle/create_test_table.sql

@@ -0,0 +1,42 @@
+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
+    property TEXT    NOT NULL,
+    side_a   REAL    NOT NULL,
+    side_b   REAL    NOT NULL,
+    side_c   REAL    NOT NULL,
+    expected BOOLEAN NOT NULL
+);
+
+INSERT INTO tests (uuid, description, property, side_a, side_b, side_c, expected)
+VALUES
+        ('8b2c43ac-7257-43f9-b552-7631a91988af','all sides are equal','equilateral',2,2,2,true),
+        ('33eb6f87-0498-4ccf-9573-7f8c3ce92b7b','any side is unequal','equilateral',2,3,2,false),
+        ('c6585b7d-a8c0-4ad8-8a34-e21d36f7ad87','no sides are equal','equilateral',5,4,6,false),
+        ('16e8ceb0-eadb-46d1-b892-c50327479251','all zero sides is not a triangle','equilateral',0,0,0,false),
+        ('3022f537-b8e5-4cc1-8f12-fd775827a00c','sides may be floats','equilateral',0.5,0.5,0.5,true),
+        ('cbc612dc-d75a-4c1c-87fc-e2d5edd70b71','last two sides are equal','isosceles',3,4,4,true),
+        ('e388ce93-f25e-4daf-b977-4b7ede992217','first two sides are equal','isosceles',4,4,3,true),
+        ('d2080b79-4523-4c3f-9d42-2da6e81ab30f','first and last sides are equal','isosceles',4,3,4,true),
+        ('8d71e185-2bd7-4841-b7e1-71689a5491d8','equilateral triangles are also isosceles','isosceles',4,4,4,true),
+        ('840ed5f8-366f-43c5-ac69-8f05e6f10bbb','no sides are equal','isosceles',2,3,4,false),
+        ('2eba0cfb-6c65-4c40-8146-30b608905eae','first triangle inequality violation','isosceles',1,1,3,false),
+        ('278469cb-ac6b-41f0-81d4-66d9b828f8ac','second triangle inequality violation','isosceles',1,3,1,false),
+        ('90efb0c7-72bb-4514-b320-3a3892e278ff','third triangle inequality violation','isosceles',3,1,1,false),
+        ('adb4ee20-532f-43dc-8d31-e9271b7ef2bc','sides may be floats','isosceles',0.5,0.4,0.5,true),
+        ('e8b5f09c-ec2e-47c1-abec-f35095733afb','no sides are equal','scalene',5,4,6,true),
+        ('2510001f-b44d-4d18-9872-2303e7977dc1','all sides are equal','scalene',4,4,4,false),
+        ('c6e15a92-90d9-4fb3-90a2-eef64f8d3e1e','first and second sides are equal','scalene',4,4,3,false),
+        ('3da23a91-a166-419a-9abf-baf4868fd985','first and third sides are equal','scalene',3,4,3,false),
+        ('b6a75d98-1fef-4c42-8e9a-9db854ba0a4d','second and third sides are equal','scalene',4,3,3,false),
+        ('70ad5154-0033-48b7-af2c-b8d739cd9fdc','may not violate triangle inequality','scalene',7,3,2,false),
+        ('26d9d59d-f8f1-40d3-ad58-ae4d54123d7d','sides may be floats','scalene',0.5,0.4,0.6,true);

exercises/practice/triangle/data.csv

@@ -0,0 +1,21 @@
+"equilateral",2,2,2,""
+"equilateral",2,3,2,""
+"equilateral",5,4,6,""
+"equilateral",0,0,0,""
+"equilateral",0.5,0.5,0.5,""
+"isosceles",3,4,4,""
+"isosceles",4,4,3,""
+"isosceles",4,3,4,""
+"isosceles",4,4,4,""
+"isosceles",2,3,4,""
+"isosceles",1,1,3,""
+"isosceles",1,3,1,""
+"isosceles",3,1,1,""
+"isosceles",0.5,0.4,0.5,""
+"scalene",5,4,6,""
+"scalene",4,4,4,""
+"scalene",4,4,3,""
+"scalene",3,4,3,""
+"scalene",4,3,3,""
+"scalene",7,3,2,""
+"scalene",0.5,0.4,0.6,""

exercises/practice/triangle/triangle.sql

@@ -0,0 +1,10 @@
+-- Schema:
+-- CREATE TABLE triangle (
+--     property TEXT    NOT NULL,
+--     side_a   REAL    NOT NULL,
+--     side_b   REAL    NOT NULL,
+--     side_c   REAL    NOT NULL,
+--     result   BOOLEAN
+-- );
+--
+-- Task: update the triangle and set result based on the property, side_a, side_b and side_c columns.

exercises/practice/triangle/triangle_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 ./triangle.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 property, side_a, side_b, side_c, result FROM triangle) AS actual
+WHERE (actual.property, actual.side_a, actual.side_b, actual.side_c, actual.result) = (tests.property, tests.side_a, tests.side_b, tests.side_c, tests.expected);
+
+-- Update message for failed tests to give helpful information:
+UPDATE tests
+SET message = (
+    'Result for "'
+    || PRINTF('property=''%s'', a=%g, b=%g, c=%g', actual.property, actual.side_a, actual.side_b, actual.side_c)
+    || '"'
+    || ' is <' || COALESCE(actual.result, 'NULL')
+    || '> but should be <' || tests.expected || '>'
+)
+FROM (SELECT property, side_a, side_b, side_c, result FROM triangle) AS actual
+WHERE (actual.property, actual.side_a, actual.side_b, actual.side_c) = (tests.property, tests.side_a, tests.side_b, tests.side_c) 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;