Add darts exercise (#219)

config.json

@@ -105,6 +105,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "darts",
+        "name": "Darts",
+        "uuid": "6b18a69a-2a24-4db1-bd84-fe599e74443f",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "difference-of-squares",
         "name": "Difference of Squares",

exercises/practice/darts/.docs/instructions.md

@@ -0,0 +1,31 @@
+# Instructions
+
+Calculate the points scored in a single toss of a Darts game.
+
+[Darts][darts] is a game where players throw darts at a [target][darts-target].
+
+In our particular instance of the game, the target rewards 4 different amounts of points, depending on where the dart lands:
+
+![Our dart scoreboard with values from a complete miss to a bullseye](https://assets.exercism.org/images/exercises/darts/darts-scoreboard.svg)
+
+- If the dart lands outside the target, player earns no points (0 points).
+- If the dart lands in the outer circle of the target, player earns 1 point.
+- If the dart lands in the middle circle of the target, player earns 5 points.
+- If the dart lands in the inner circle of the target, player earns 10 points.
+
+The outer circle has a radius of 10 units (this is equivalent to the total radius for the entire target), the middle circle a radius of 5 units, and the inner circle a radius of 1.
+Of course, they are all centered at the same point — that is, the circles are [concentric][] defined by the coordinates (0, 0).
+
+Given a point in the target (defined by its [Cartesian coordinates][cartesian-coordinates] `x` and `y`, where `x` and `y` are [real][real-numbers]), calculate the correct score earned by a dart landing at that point.
+
+## Credit
+
+The scoreboard image was created by [habere-et-dispertire][habere-et-dispertire] using [Inkscape][inkscape].
+
+[darts]: https://en.wikipedia.org/wiki/Darts
+[darts-target]: https://en.wikipedia.org/wiki/Darts#/media/File:Darts_in_a_dartboard.jpg
+[concentric]: https://mathworld.wolfram.com/ConcentricCircles.html
+[cartesian-coordinates]: https://www.mathsisfun.com/data/cartesian-coordinates.html
+[real-numbers]: https://www.mathsisfun.com/numbers/real-numbers.html
+[habere-et-dispertire]: https://exercism.org/profiles/habere-et-dispertire
+[inkscape]: https://en.wikipedia.org/wiki/Inkscape

exercises/practice/darts/.gitignore

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

exercises/practice/darts/.meta/config.json

@@ -0,0 +1,18 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "src/darts.lfe"
+    ],
+    "test": [
+      "test/darts-tests.lfe"
+    ],
+    "example": [
+      ".meta/example.lfe"
+    ]
+  },
+  "blurb": "Calculate the points scored in a single toss of a Darts game.",
+  "source": "Inspired by an exercise created by a professor Della Paolera in Argentina"
+}

exercises/practice/darts/.meta/example.lfe

@@ -0,0 +1,12 @@
+(defmodule darts
+  (export (score 2)))
+
+(defun score (x y)
+  (assign-score (math:sqrt (+ (* x x)
+                              (* y y)))))
+
+(defun assign-score
+  ((dist) (when (=< dist 1)) 10)
+  ((dist) (when (=< dist 5)) 5)
+  ((dist) (when (=< dist 10)) 1)
+  ((_) 0))

exercises/practice/darts/.meta/tests.toml

@@ -0,0 +1,49 @@
+# 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.
+
+[9033f731-0a3a-4d9c-b1c0-34a1c8362afb]
+description = "Missed target"
+
+[4c9f6ff4-c489-45fd-be8a-1fcb08b4d0ba]
+description = "On the outer circle"
+
+[14378687-ee58-4c9b-a323-b089d5274be8]
+description = "On the middle circle"
+
+[849e2e63-85bd-4fed-bc3b-781ae962e2c9]
+description = "On the inner circle"
+
+[1c5ffd9f-ea66-462f-9f06-a1303de5a226]
+description = "Exactly on center"
+
+[b65abce3-a679-4550-8115-4b74bda06088]
+description = "Near the center"
+
+[66c29c1d-44f5-40cf-9927-e09a1305b399]
+description = "Just within the inner circle"
+
+[d1012f63-c97c-4394-b944-7beb3d0b141a]
+description = "Just outside the inner circle"
+
+[ab2b5666-b0b4-49c3-9b27-205e790ed945]
+description = "Just within the middle circle"
+
+[70f1424e-d690-4860-8caf-9740a52c0161]
+description = "Just outside the middle circle"
+
+[a7dbf8db-419c-4712-8a7f-67602b69b293]
+description = "Just within the outer circle"
+
+[e0f39315-9f9a-4546-96e4-a9475b885aa7]
+description = "Just outside the outer circle"
+
+[045d7d18-d863-4229-818e-b50828c75d19]
+description = "Asymmetric position between the inner and middle circles"

exercises/practice/darts/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/darts/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/darts/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/darts/src/darts.app.src

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

exercises/practice/darts/src/darts.lfe

@@ -0,0 +1,4 @@
+(defmodule darts
+  (export (score 2)))
+
+; Please implement the score function.

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

@@ -0,0 +1,44 @@
+(defmodule darts-tests
+  (behaviour ltest-unit)
+  (export all))
+
+(include-lib "ltest/include/ltest-macros.lfe")
+
+(deftest missed-target
+  (is-equal 0 (darts:score -9 9)))
+
+(deftest on-the-outer-circle
+  (is-equal 1 (darts:score 0 10)))
+
+(deftest on-the-middle-circle
+  (is-equal 5 (darts:score -5 0)))
+
+(deftest on-the-inner-circle
+  (is-equal 10 (darts:score 0 -1)))
+
+(deftest exactly-on-center
+  (is-equal 10 (darts:score 0 0)))
+
+(deftest near-the-center
+  (is-equal 10 (darts:score -0.1 -0.1)))
+
+(deftest just-within-the-inner-circle
+  (is-equal 10 (darts:score 0.7 0.7)))
+
+(deftest just-outside-the-inner-circle
+  (is-equal 5 (darts:score 0.8 -0.8)))
+
+(deftest just-within-the-middle-circle
+  (is-equal 5 (darts:score -3.5 3.5)))
+
+(deftest just-outside-the-middle-circle
+  (is-equal 1 (darts:score -3.6 -3.6)))
+
+(deftest just-within-the-outer-circle
+  (is-equal 1 (darts:score -7.0 7.0)))
+
+(deftest just-outside-the-outer-circle
+  (is-equal 0 (darts:score 7.1 -7.1)))
+
+(deftest asymmetric-position-between-the-inner-and-middle-circles
+  (is-equal 5 (darts:score 0.5 -4)))