Add triangle exercise

config.json

@@ -224,6 +224,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "triangle",
+        "name": "Triangle",
+        "uuid": "b8631f1c-0023-4746-bdc1-b54e75fc9530",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "flatten-array",
         "name": "Flatten Array",

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": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "src/Triangle.idr"
+    ],
+    "test": [
+      "test/src/Main.idr"
+    ],
+    "example": [
+      "example/Triangle.idr"
+    ]
+  },
+  "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/tests.toml

@@ -0,0 +1,76 @@
+# 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"
+include = false
+
+[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"
+include = false
+
+[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"
+include = false

exercises/practice/triangle/example/Triangle.idr

@@ -0,0 +1,27 @@
+module Triangle
+
+import Data.Vect
+
+isTriangle : Vect 3 Integer -> Bool
+isTriangle (first :: second :: third :: nil) = (first <= second + third) &&
+                                               (second <= first + third) &&
+                                               (third <= first + second)
+
+-- number of distinct values
+cardinality : Vect 3 Integer -> Integer
+cardinality (first :: second :: third :: nil) =
+    if (first == second) && (first == third) then 1
+    else if (first == second) || (first == third) || (second == third) then 2
+    else 3
+
+export
+isEquilateral : Vect 3 Integer -> Bool
+isEquilateral sides = (isTriangle sides) && (cardinality sides == 1)
+
+export
+isIsosceles : Vect 3 Integer -> Bool
+isIsosceles sides = (isTriangle sides) && (cardinality sides == 2)
+
+export
+isScalene : Vect 3 Integer -> Bool
+isScalene sides = (isTriangle sides) && (cardinality sides == 3)

exercises/practice/triangle/pack.toml

@@ -0,0 +1,10 @@
+[custom.all.triangle]
+type = "local"
+path = "."
+ipkg = "triangle.ipkg"
+test = "test/test.ipkg"
+
+[custom.all.triangle-test]
+type = "local"
+path = "test"
+ipkg = "test.ipkg"

exercises/practice/triangle/src/Triangle.idr

@@ -0,0 +1,16 @@
+module Triangle
+
+import Data.Vect
+
+export
+isEquilateral : Vect 3 Integer -> Bool
+isEquilateral sides = ?isEquilateral_rhs
+
+export
+isIsosceles : Vect 3 Integer -> Bool
+isIsosceles sides = ?isIsosceles_rhs
+
+export
+isScalene : Vect 3 Integer -> Bool
+isScalene sides = ?isScalene_rhs
+

exercises/practice/triangle/test/src/Main.idr

@@ -0,0 +1,37 @@
+module Main
+
+import System
+import Tester
+import Tester.Runner
+
+import Triangle
+
+tests : List Test
+tests =
+  [ test "all sides are equal"                      (assert $       isEquilateral [2, 2, 2])
+  , test "any side is unequal"                      (assert $ not $ isEquilateral [2, 3, 2])
+  , test "no sides are equal"                       (assert $ not $ isEquilateral [5, 4, 6])
+  , test "all zero sides is not a triangle"         (assert $ not $ isEquilateral [0, 0, 0])
+  , test "last two sides are equal"                 (assert $       isIsosceles [3, 4, 4])
+  , test "first two sides are equal"                (assert $       isIsosceles [4, 4, 3])
+  , test "first and last sides are equal"           (assert $       isIsosceles [4, 3, 4])
+  , test "equilateral triangles are also isosceles" (assert $       isIsosceles [4, 4, 4])
+  , test "no sides are equal"                       (assert $ not $ isIsosceles [2, 3, 4])
+  , test "first triangle inequality violation"      (assert $ not $ isIsosceles [1, 1, 3])
+  , test "second triangle inequality violation"     (assert $ not $ isIsosceles [1, 3, 1])
+  , test "third triangle inequality violation"      (assert $ not $ isIsosceles [3, 1, 1])
+  , test "no sides are equal"                       (assert $       isScalene [5, 4, 6])
+  , test "all sides are equal"                      (assert $ not $ isScalene [4, 4, 4])
+  , test "first and second sides are equal"         (assert $ not $ isScalene [4, 4, 3])
+  , test "first and third sides are equal"          (assert $ not $ isScalene [3, 4, 3])
+  , test "second and third sides are equal"         (assert $ not $ isScalene [4, 3, 3])
+  , test "may not violate triangle inequality"      (assert $ not $ isScalene [7, 3, 2])
+  ]
+
+export
+main : IO ()
+main = do
+  success <- runTests tests
+  if success
+     then putStrLn "All tests passed"
+     else exitFailure

exercises/practice/triangle/test/test.ipkg

@@ -0,0 +1,6 @@
+package triangle-test
+depends = triangle
+  , tester
+main = Main
+executable = "triangle-test"
+sourcedir = "src"

exercises/practice/triangle/triangle.ipkg

@@ -0,0 +1,3 @@
+package triangle
+modules = Triangle
+sourcedir = "src"

generators/exercises/triangle.py

@@ -0,0 +1,11 @@
+
+def generate_test(case):
+    property = case["property"].capitalize()
+    sides = case["input"]["sides"]
+    expected = case["expected"]
+    if expected:
+        prefix = 'assert $      '
+    else:
+        prefix = 'assert $ not $'
+
+    return f'{prefix} is{property} {sides}'