Add Roman numerals practice exercise (#193)

config.json

@@ -351,6 +351,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "roman-numerals",
+        "name": "Roman Numerals",
+        "uuid": "461223ea-e86b-4b94-9e7a-ac3ec1aa8a12",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
       }
     ]
   },

exercises/practice/roman-numerals/.docs/instructions.md

@@ -0,0 +1,12 @@
+# Introduction
+
+Your task is to convert a number from Arabic numerals to Roman numerals.
+
+For this exercise, we are only concerned about traditional Roman numerals, in which the largest number is MMMCMXCIX (or 3,999).
+
+~~~~exercism/note
+There are lots of different ways to convert between Arabic and Roman numerals.
+We recommend taking a naive approach first to familiarise yourself with the concept of Roman numerals and then search for more efficient methods.
+
+Make sure to check out our Deep Dive video at the end to explore the different approaches you can take!
+~~~~

exercises/practice/roman-numerals/.docs/introduction.md

@@ -0,0 +1,59 @@
+# Description
+
+Today, most people in the world use Arabic numerals (0–9).
+But if you travelled back two thousand years, you'd find that most Europeans were using Roman numerals instead.
+
+To write a Roman numeral we use the following Latin letters, each of which has a value:
+
+| M    | D   | C   | L   | X   | V   | I   |
+| ---- | --- | --- | --- | --- | --- | --- |
+| 1000 | 500 | 100 | 50  | 10  | 5   | 1   |
+
+A Roman numeral is a sequence of these letters, and its value is the sum of the letters' values.
+For example, `XVIII` has the value 18 (`10 + 5 + 1 + 1 + 1 = 18`).
+
+There's one rule that makes things trickier though, and that's that **the same letter cannot be used more than three times in succession**.
+That means that we can't express numbers such as 4 with the seemingly natural `IIII`.
+Instead, for those numbers, we use a subtraction method between two letters.
+So we think of `4` not as `1 + 1 + 1 + 1` but instead as `5 - 1`.
+And slightly confusingly to our modern thinking, we write the smaller number first.
+This applies only in the following cases: 4 (`IV`), 9 (`IX`), 40 (`XL`), 90 (`XC`), 400 (`CD`) and 900 (`CM`).
+
+Order matters in Roman numerals!
+Letters (and the special compounds above) must be ordered by decreasing value from left to right.
+
+Here are some examples:
+
+```text
+ 105 => CV
+---- => --
+ 100 => C
++  5 =>  V
+```
+
+```text
+ 106 => CVI
+---- => --
+ 100 => C
++  5 =>  V
++  1 =>   I
+```
+
+```text
+ 104 => CIV
+---- => ---
+ 100 => C
++  4 =>  IV
+```
+
+And a final more complex example:
+
+```text
+ 1996 => MCMXCVI
+----- => -------
+ 1000 => M
++ 900 =>  CM
++  90 =>    XC
++   5 =>      V
++   1 =>       I
+```

exercises/practice/roman-numerals/.meta/config.json

@@ -0,0 +1,22 @@
+{
+  "authors": [
+    "kahgoh"
+  ],
+  "files": {
+    "solution": [
+      "src/roman-numerals.lfe"
+    ],
+    "test": [
+      "test/roman-numerals-tests.lfe"
+    ],
+    "example": [
+      ".meta/example.lfe"
+    ],
+    "invalidator": [
+      "rebar.config"
+    ]
+  },
+  "blurb": "Convert modern Arabic numbers into Roman numerals.",
+  "source": "The Roman Numeral Kata",
+  "source_url": "https://codingdojo.org/kata/RomanNumerals/"
+}

exercises/practice/roman-numerals/.meta/example.lfe

@@ -0,0 +1,29 @@
+(defmodule roman-numerals
+  (export (roman 1))
+)
+
+(defun numerals () '(("I" "V" "X")
+                    ("X" "L" "C")
+                    ("C" "D" "M")
+                    ("M" "" ""))
+)
+
+(defun roman (value) (conv value "" (numerals)))
+
+(defun conv 
+  ((_remaining acc []) acc)
+  ((remaining acc (cons (list ones fives tens) next)) (conv (div remaining 10) (++ (roman-digit (rem remaining 10) ones fives tens) acc) next))
+)
+
+(defun roman-digit
+  ((0 _ones _fives _tens) "") 
+  ((1 ones _fives tens) ones)
+  ((2 ones _fives tens) (++ ones ones)) 
+  ((3 ones _fives _tens) (++ ones ones ones))
+  ((4 ones fives _tens) (++ ones fives))
+  ((5 _ones fives _tens) fives)
+  ((6 ones fives _tens) (++ fives ones))
+  ((7 ones fives _tens) (++ fives ones ones))
+  ((8 ones fives _tens) (++ fives ones ones ones))
+  ((9 ones _fives tens) (++ ones tens))
+)

exercises/practice/roman-numerals/.meta/tests.toml

@@ -0,0 +1,88 @@
+# 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.
+
+[19828a3a-fbf7-4661-8ddd-cbaeee0e2178]
+description = "1 is I"
+
+[f088f064-2d35-4476-9a41-f576da3f7b03]
+description = "2 is II"
+
+[b374a79c-3bea-43e6-8db8-1286f79c7106]
+description = "3 is III"
+
+[05a0a1d4-a140-4db1-82e8-fcc21fdb49bb]
+description = "4 is IV"
+
+[57c0f9ad-5024-46ab-975d-de18c430b290]
+description = "5 is V"
+
+[20a2b47f-e57f-4797-a541-0b3825d7f249]
+description = "6 is VI"
+
+[ff3fb08c-4917-4aab-9f4e-d663491d083d]
+description = "9 is IX"
+
+[6d1d82d5-bf3e-48af-9139-87d7165ed509]
+description = "16 is XVI"
+
+[2bda64ca-7d28-4c56-b08d-16ce65716cf6]
+description = "27 is XXVII"
+
+[a1f812ef-84da-4e02-b4f0-89c907d0962c]
+description = "48 is XLVIII"
+
+[607ead62-23d6-4c11-a396-ef821e2e5f75]
+description = "49 is XLIX"
+
+[d5b283d4-455d-4e68-aacf-add6c4b51915]
+description = "59 is LIX"
+
+[4465ffd5-34dc-44f3-ada5-56f5007b6dad]
+description = "66 is LXVI"
+
+[46b46e5b-24da-4180-bfe2-2ef30b39d0d0]
+description = "93 is XCIII"
+
+[30494be1-9afb-4f84-9d71-db9df18b55e3]
+description = "141 is CXLI"
+
+[267f0207-3c55-459a-b81d-67cec7a46ed9]
+description = "163 is CLXIII"
+
+[902ad132-0b4d-40e3-8597-ba5ed611dd8d]
+description = "166 is CLXVI"
+
+[cdb06885-4485-4d71-8bfb-c9d0f496b404]
+description = "402 is CDII"
+
+[6b71841d-13b2-46b4-ba97-dec28133ea80]
+description = "575 is DLXXV"
+
+[dacb84b9-ea1c-4a61-acbb-ce6b36674906]
+description = "666 is DCLXVI"
+
+[432de891-7fd6-4748-a7f6-156082eeca2f]
+description = "911 is CMXI"
+
+[e6de6d24-f668-41c0-88d7-889c0254d173]
+description = "1024 is MXXIV"
+
+[efbe1d6a-9f98-4eb5-82bc-72753e3ac328]
+description = "1666 is MDCLXVI"
+
+[bb550038-d4eb-4be2-a9ce-f21961ac3bc6]
+description = "3000 is MMM"
+
+[3bc4b41c-c2e6-49d9-9142-420691504336]
+description = "3001 is MMMI"
+
+[4e18e96b-5fbb-43df-a91b-9cb511fe0856]
+description = "3999 is MMMCMXCIX"

exercises/practice/roman-numerals/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/roman-numerals/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/roman-numerals/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/roman-numerals/src/roman-numerals.app.src

@@ -0,0 +1,11 @@
+%% -*- erlang -*-
+{application, 'roman-numerals',
+ [{description, "Write a function to convert from normal numbers to Roman Numerals."},
+  {vsn, "0.0.1"},
+  {modules,
+   ['roman-numerals']},
+  {registered, []},
+  {applications,
+   [kernel, stdlib]},
+  {included_applications, []},
+  {env, []}]}.

exercises/practice/roman-numerals/src/roman-numerals.lfe

@@ -0,0 +1,5 @@
+(defmodule roman-numerals
+  (export (roman 1))
+)
+
+  ; Please implement the roman function

exercises/practice/roman-numerals/test/roman-numerals-tests.lfe

@@ -0,0 +1,83 @@
+(defmodule roman-numerals-tests
+  (behaviour ltest-unit)
+  (export all))
+
+(include-lib "ltest/include/ltest-macros.lfe")
+
+(deftest 1-is-I
+  (is-equal "I" (roman-numerals:roman 1)))
+
+(deftest 2-is-II
+  (is-equal "II" (roman-numerals:roman 2)))
+
+(deftest 3-is-III
+  (is-equal "III" (roman-numerals:roman 3)))
+
+(deftest 4-is-IV
+  (is-equal "IV" (roman-numerals:roman 4)))
+
+(deftest 5-is-V
+  (is-equal "V" (roman-numerals:roman 5)))
+
+(deftest 6-is-VI
+  (is-equal "VI" (roman-numerals:roman 6)))
+
+(deftest 9-is-IX
+  (is-equal "IX" (roman-numerals:roman 9)))
+
+(deftest 16-is-XVI
+  (is-equal "XVI" (roman-numerals:roman 16)))
+
+(deftest 27-is-XXVII
+  (is-equal "XXVII" (roman-numerals:roman 27)))
+
+(deftest 48-is-XLVIII
+  (is-equal "XLVIII" (roman-numerals:roman 48)))
+
+(deftest 49-is-XLIX
+  (is-equal "XLIX" (roman-numerals:roman 49)))
+
+(deftest 59-is-LIX
+  (is-equal "LIX" (roman-numerals:roman 59)))
+
+(deftest 66-is-LXVI
+  (is-equal "LXVI" (roman-numerals:roman 66)))
+
+(deftest 93-is-XCIII
+  (is-equal "XCIII" (roman-numerals:roman 93)))
+
+(deftest 141-is-CXLI
+  (is-equal "CXLI" (roman-numerals:roman 141)))
+
+(deftest 163-is-CLXIII
+  (is-equal "CLXIII" (roman-numerals:roman 163)))
+
+(deftest 166-is-CLXVI
+  (is-equal "CLXVI" (roman-numerals:roman 166)))
+
+(deftest 402-is-CDII
+  (is-equal "CDII" (roman-numerals:roman 402)))
+
+(deftest 575-is-DLXXV
+  (is-equal "DLXXV" (roman-numerals:roman 575)))
+
+(deftest 666-is-DCLXVI
+  (is-equal "DCLXVI" (roman-numerals:roman 666)))
+
+(deftest 911-is-CMXI
+  (is-equal "CMXI" (roman-numerals:roman 911)))
+
+(deftest 1024-is-MXXIV
+  (is-equal "MXXIV" (roman-numerals:roman 1024)))
+
+(deftest 1666-is-MDCLXVI
+  (is-equal "MDCLXVI" (roman-numerals:roman 1666)))
+
+(deftest 3000-is-MMM
+  (is-equal "MMM" (roman-numerals:roman 3000)))
+
+(deftest 3001-is-MMMI
+  (is-equal "MMMI" (roman-numerals:roman 3001)))
+
+(deftest 3999-is-MMMCMXCIX
+  (is-equal "MMMCMXCIX" (roman-numerals:roman 3999)))