Add perfect-numbers (#250)

config.json

@@ -180,6 +180,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "perfect-numbers",
+        "name": "Perfect Numbers",
+        "uuid": "659d24f5-1e6d-4622-a2dc-177aecc10fae",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "resistor-color",
         "name": "Resistor Color",

exercises/practice/perfect-numbers/.docs/instructions.md

@@ -0,0 +1,39 @@
+# Instructions
+
+Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.
+
+The Greek mathematician [Nicomachus][nicomachus] devised a classification scheme for positive integers, identifying each as belonging uniquely to the categories of [perfect](#perfect), [abundant](#abundant), or [deficient](#deficient) based on their [aliquot sum][aliquot-sum].
+The _aliquot sum_ is defined as the sum of the factors of a number not including the number itself.
+For example, the aliquot sum of `15` is `1 + 3 + 5 = 9`.
+
+## Perfect
+
+A number is perfect when it equals its aliquot sum.
+For example:
+
+- `6` is a perfect number because `1 + 2 + 3 = 6`
+- `28` is a perfect number because `1 + 2 + 4 + 7 + 14 = 28`
+
+## Abundant
+
+A number is abundant when it is less than its aliquot sum.
+For example:
+
+- `12` is an abundant number because `1 + 2 + 3 + 4 + 6 = 16`
+- `24` is an abundant number because `1 + 2 + 3 + 4 + 6 + 8 + 12 = 36`
+
+## Deficient
+
+A number is deficient when it is greater than its aliquot sum.
+For example:
+
+- `8` is a deficient number because `1 + 2 + 4 = 7`
+- Prime numbers are deficient
+
+## Task
+
+Implement a way to determine whether a given number is [perfect](#perfect).
+Depending on your language track, you may also need to implement a way to determine whether a given number is [abundant](#abundant) or [deficient](#deficient).
+
+[nicomachus]: https://en.wikipedia.org/wiki/Nicomachus
+[aliquot-sum]: https://en.wikipedia.org/wiki/Aliquot_sum

exercises/practice/perfect-numbers/.gitignore

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

exercises/practice/perfect-numbers/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "src/perfect-numbers.lfe"
+    ],
+    "test": [
+      "test/perfect-numbers-tests.lfe"
+    ],
+    "example": [
+      ".meta/example.lfe"
+    ]
+  },
+  "blurb": "Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.",
+  "source": "Taken from Chapter 2 of Functional Thinking by Neal Ford.",
+  "source_url": "https://www.oreilly.com/library/view/functional-thinking/9781449365509/"
+}

exercises/practice/perfect-numbers/.meta/example.lfe

@@ -0,0 +1,21 @@
+(defmodule perfect-numbers
+  (export (classify 1)))
+
+(defun classify (number)
+  (if (=< number 0)
+      'false
+      (let ((sum-of-factors (lists:sum (factors-of number))))
+        (label number sum-of-factors))))
+
+(defun factors-of (number)
+  (lists:filter (lambda (x) (=:= 0 (rem number x)))
+                (lists:seq 1 (div number 2))))
+
+(defun label 
+  ((number number)
+   'perfect)
+  ((number sum) (when (< number sum))
+                'abundant)
+  ((number sum) (when (> number sum))
+                'deficient))
+

exercises/practice/perfect-numbers/.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.
+
+[163e8e86-7bfd-4ee2-bd68-d083dc3381a3]
+description = "Perfect numbers -> Smallest perfect number is classified correctly"
+
+[169a7854-0431-4ae0-9815-c3b6d967436d]
+description = "Perfect numbers -> Medium perfect number is classified correctly"
+
+[ee3627c4-7b36-4245-ba7c-8727d585f402]
+description = "Perfect numbers -> Large perfect number is classified correctly"
+
+[80ef7cf8-9ea8-49b9-8b2d-d9cb3db3ed7e]
+description = "Abundant numbers -> Smallest abundant number is classified correctly"
+
+[3e300e0d-1a12-4f11-8c48-d1027165ab60]
+description = "Abundant numbers -> Medium abundant number is classified correctly"
+
+[ec7792e6-8786-449c-b005-ce6dd89a772b]
+description = "Abundant numbers -> Large abundant number is classified correctly"
+
+[e610fdc7-2b6e-43c3-a51c-b70fb37413ba]
+description = "Deficient numbers -> Smallest prime deficient number is classified correctly"
+
+[0beb7f66-753a-443f-8075-ad7fbd9018f3]
+description = "Deficient numbers -> Smallest non-prime deficient number is classified correctly"
+
+[1c802e45-b4c6-4962-93d7-1cad245821ef]
+description = "Deficient numbers -> Medium deficient number is classified correctly"
+
+[47dd569f-9e5a-4a11-9a47-a4e91c8c28aa]
+description = "Deficient numbers -> Large deficient number is classified correctly"
+
+[a696dec8-6147-4d68-afad-d38de5476a56]
+description = "Deficient numbers -> Edge case (no factors other than itself) is classified correctly"
+
+[72445cee-660c-4d75-8506-6c40089dc302]
+description = "Invalid inputs -> Zero is rejected (as it is not a positive integer)"
+
+[2d72ce2c-6802-49ac-8ece-c790ba3dae13]
+description = "Invalid inputs -> Negative integer is rejected (as it is not a positive integer)"

exercises/practice/perfect-numbers/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/perfect-numbers/rebar.config

@@ -0,0 +1,11 @@
+{plugins, [{rebar3_lfe, "0.4.10"}]}.
+
+{provider_hooks, [{post, [{compile, {lfe, compile}}]}]}.
+
+{deps, [{lfe, "2.1.3"}]}.
+
+{profiles,
+ [{test,
+   [{eunit_compile_opts, [{src_dirs, ["src", "test"]}]},
+    {deps,
+     [{ltest, "0.13.8"}]}]}]}.

exercises/practice/perfect-numbers/rebar.lock

@@ -0,0 +1,8 @@
+{"1.2.0",
+[{<<"lfe">>,{pkg,<<"lfe">>,<<"2.1.3">>},0}]}.
+[
+{pkg_hash,[
+ {<<"lfe">>, <<"6EFCB2BBC1FFC21DC5D1C092F00EFDB397EAC889474AC5C86EDF78A3557CC730">>}]},
+{pkg_hash_ext,[
+ {<<"lfe">>, <<"4E4BAD515A169AE418FEB7374EA1C8D741FAEA9D95E266CE343B45BCC377F55B">>}]}
+].

exercises/practice/perfect-numbers/src/perfect-numbers.app.src

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

exercises/practice/perfect-numbers/src/perfect-numbers.lfe

@@ -0,0 +1,5 @@
+(defmodule perfect-numbers
+  (export (classify 1)))
+
+; Please implement the 'classify' function
+

exercises/practice/perfect-numbers/test/perfect-numbers-tests.lfe

@@ -0,0 +1,45 @@
+(defmodule perfect-numbers-tests
+  (behaviour ltest-unit)
+  (export all))
+
+(include-lib "ltest/include/ltest-macros.lfe")
+
+(deftest smallest-perfect-number
+  (is-equal 'perfect (perfect-numbers:classify 6)))
+
+(deftest medium-perfect-number
+  (is-equal 'perfect (perfect-numbers:classify 28)))
+
+(deftest large-perfect-number
+    (is-equal 'perfect (perfect-numbers:classify 33550336)))
+
+(deftest smallest-abundant-number
+    (is-equal 'abundant (perfect-numbers:classify 12)))
+
+(deftest medium-abundant-number
+    (is-equal 'abundant (perfect-numbers:classify 30)))
+
+(deftest large-abundant-number
+    (is-equal 'abundant (perfect-numbers:classify 33550335)))
+
+(deftest smallest-prime-deficient-number
+    (is-equal 'deficient (perfect-numbers:classify 2)))
+
+(deftest smallest-non-prime-deficient-number
+    (is-equal 'deficient (perfect-numbers:classify 4)))
+
+(deftest medium-deficient-number
+    (is-equal 'deficient (perfect-numbers:classify 32)))
+
+(deftest large-deficient-number
+    (is-equal 'deficient (perfect-numbers:classify 33550337)))
+
+(deftest edge-case-number-no-factors-other-than-self
+    (is-equal 'deficient (perfect-numbers:classify 1)))
+
+(deftest zero-is-rejected
+    (is-not (perfect-numbers:classify 0)))
+
+(deftest negative-integer-is-rejected
+    (is-not (perfect-numbers:classify -1)))
+