Add triangle (#222)

config.json

@@ -282,6 +282,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "triangle",
+        "name": "Triangle",
+        "uuid": "82577254-d303-4996-9596-ca88428e6a9a",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "binary-search",
         "name": "Binary Search",

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

@@ -0,0 +1,3 @@
+# Instructions append
+
+For this exercise, scalene triangles are instead defined as those where only two sides are equal. Equilateral and isosceles triangles are still defined as above.

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/.gitignore

@@ -0,0 +1,11 @@
+## -*- conf -*-
+.rebar3
+_build/
+ebin/
+erl_crash.dump
+rebar3.crashdump
+
+tmp
+bin/configlet
+bin/configlet.exe
+CHECKLIST

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

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "src/triangle.lfe"
+    ],
+    "test": [
+      "test/triangle-tests.lfe"
+    ],
+    "example": [
+      ".meta/example.lfe"
+    ]
+  },
+  "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.lfe

@@ -0,0 +1,22 @@
+(defmodule triangle
+  (export (kind 3)))
+
+(defun kind
+    ((A B C) (when (and (=< A 0)
+                        (=< B 0)
+                        (=< C 0)))
+        'false)
+    ((A B C) (when (or (>= C (+ A B))
+                       (>= B (+ A C))
+                       (>= A (+ B C))))
+        'false)
+    ((A A A)
+        'equilateral)
+    ((A A _)
+        'isosceles)
+    ((A _ A)
+        'isosceles)
+    ((_ A A)
+        'isosceles)
+    ((_ _ _)
+        'scalene))

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

@@ -0,0 +1,81 @@
+# 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"
+include = false
+
+[c6585b7d-a8c0-4ad8-8a34-e21d36f7ad87]
+description = "equilateral triangle -> no sides are equal"
+include = false
+
+[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"
+include = false
+
+[840ed5f8-366f-43c5-ac69-8f05e6f10bbb]
+description = "isosceles triangle -> no sides are equal"
+include = false
+
+[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"
+include = false
+
+[c6e15a92-90d9-4fb3-90a2-eef64f8d3e1e]
+description = "scalene triangle -> first and second sides are equal"
+include = false
+
+[3da23a91-a166-419a-9abf-baf4868fd985]
+description = "scalene triangle -> first and third sides are equal"
+include = false
+
+[b6a75d98-1fef-4c42-8e9a-9db854ba0a4d]
+description = "scalene triangle -> second and third sides are equal"
+include = false
+
+[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/Makefile

@@ -0,0 +1,21 @@
+ERL    := $(shell which erl)
+REBAR3 := $(shell which rebar3)
+
+null  :=
+space := $(null) #
+comma := ,
+
+ifeq ($(ERL),)
+  $(error Can't find Erlang executable 'erl')
+else ifeq ($(REBAR3),)
+  $(error Can't find rebar3)
+endif
+
+compile: ; $(REBAR3) compile
+
+clean: ; $(REBAR3) clean
+
+.PHONY: test
+test:
+	$(REBAR3) eunit \
+	-m $(subst $(space),$(comma),$(basename $(notdir $(wildcard test/*.lfe))))

exercises/practice/triangle/rebar.config

@@ -0,0 +1,11 @@
+{plugins, [{rebar3_lfe, "0.4.3"}]}.
+
+{provider_hooks, [{post, [{compile, {lfe, compile}}]}]}.
+
+{deps, [{lfe, "2.1.1"}]}.
+
+{profiles,
+ [{test,
+   [{eunit_compile_opts, [{src_dirs, ["src", "test"]}]},
+    {deps,
+     [{ltest, "0.13.3"}]}]}]}.

exercises/practice/triangle/rebar.lock

@@ -0,0 +1,8 @@
+{"1.2.0",
+[{<<"lfe">>,{pkg,<<"lfe">>,<<"2.1.1">>},0}]}.
+[
+{pkg_hash,[
+ {<<"lfe">>, <<"4A888B26172D198DC7A5AFEB897E8248AF7D56E1638D9C8249AAF933AE811B96">>}]},
+{pkg_hash_ext,[
+ {<<"lfe">>, <<"C484D3B655D40DED58BC41B17B22F173711C681BF36063A234A9BAA9506947E1">>}]}
+].

exercises/practice/triangle/src/triangle.app.src

@@ -0,0 +1,11 @@
+%% -*- erlang -*-
+{application, 'triangle',
+ [{description, ""},
+  {vsn, "0.0.1"},
+  {modules,
+   ['triangle']},
+  {registered, []},
+  {applications,
+   [kernel, stdlib]},
+  {included_applications, []},
+  {env, []}]}.

exercises/practice/triangle/src/triangle.lfe

@@ -0,0 +1,4 @@
+(defmodule triangle
+  (export (kind 3)))
+
+    ; Please implement the kind function.

exercises/practice/triangle/test/triangle-tests.lfe

@@ -0,0 +1,44 @@
+(defmodule triangle-tests
+  (behaviour ltest-unit)
+  (export all))
+
+(include-lib "ltest/include/ltest-macros.lfe")
+
+(deftest equilateral-triangle-all-sides-are-equal
+  (is-equal (triangle:kind 2 2 2) 'equilateral))
+
+(deftest equilateral-triangle-all-zero-sides-is-not-a-triangle
+  (is-not (triangle:kind 0 0 0)))
+
+(deftest equilateral-triangle-sides-may-be-floats
+  (is-equal (triangle:kind 0.5 0.5 0.5) 'equilateral))
+
+(deftest isosceles-triangle-last-two-sides-are-equal
+  (is-equal (triangle:kind 3 4 4) 'isosceles))
+
+(deftest isosceles-triangle-first-two-sides-are-equal
+  (is-equal (triangle:kind 4 4 3) 'isosceles))
+
+(deftest isosceles-triangle-first-and-last-sides-are-equal
+  (is-equal (triangle:kind 4 3 4) 'isosceles))
+
+(deftest isosceles-first-triangle-inequality
+  (is-not (triangle:kind 1 2 3)))
+
+(deftest isosceles-second-triangle-inequality
+  (is-not (triangle:kind 1 3 1)))
+
+(deftest isosceles-third-triangle-inequality
+  (is-not (triangle:kind 3 1 1)))
+
+(deftest isosceles-may-be-floats
+  (is-equal (triangle:kind 0.5 0.4 0.5) 'isosceles))
+
+(deftest scalene-no-sides-are-equal
+  (is-equal (triangle:kind 5 4 6) 'scalene))
+
+(deftest scalene-may-not-violate-triangle-inequality
+  (is-not (triangle:kind 7 3 2)))
+
+(deftest scalene-may-be-floats
+  (is-equal (triangle:kind 0.5 0.4 0.6) 'scalene))