From 9fb2fe18ccb793b31a1118ab68f00190ee3c11f3 Mon Sep 17 00:00:00 2001
From: "Ivan I. Ovchinnikov" <mail@iovchinnikov.ru>
Date: Mon, 13 Feb 2023 12:14:07 +0300
Subject: [PATCH] wip1 mobius

---
 src/mobius.erl       | 48 ++++++++++++++++++++++++++++++++++++++++++++
 test/mobius_test.erl | 24 ++++++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 src/mobius.erl
 create mode 100644 test/mobius_test.erl

diff --git a/src/mobius.erl b/src/mobius.erl
new file mode 100644
index 0000000..9c502f0
--- /dev/null
+++ b/src/mobius.erl
@@ -0,0 +1,48 @@
+%%%-------------------------------------------------------------------
+%%% @author ivan-igorevich
+%%% @copyright (C) 2023, self
+%%% @doc
+%%%
+%%% @end
+%%% Created : 13. Feb 2023 8:49 AM
+%%%-------------------------------------------------------------------
+-module(mobius).
+-author("ivan-igorevich").
+
+%% API
+-export([is_prime/1, prime_factors/1, say/0]).
+
+%% region is_prime
+is_prime(N) when N < 2 ->
+  false;
+is_prime(N) ->
+  is_prime(N, 2, trunc(math:sqrt(N)) + 1).
+
+is_prime(_, Max, Max) ->
+  true;
+is_prime(N, I, Max) ->
+  if
+    N rem I =:= 0 ->
+      false;
+    true ->
+      is_prime(N, I + 1, Max)
+  end.
+%% endregion
+
+%region factor
+prime_factors(N) ->
+  prime_factors(N, 2, []).
+
+prime_factors(X, N, Primes) when X rem N == 0 ->
+  prime_factors(trunc(X / N), 2, [N | Primes]);
+prime_factors(X, N, Primes) ->
+  case N < math:sqrt(X) + 1 of
+    true ->
+      prime_factors(X, N + 1, Primes);
+    false ->
+      [X | Primes]
+  end.
+%endregion
+
+say() -> io:format("The result is: ~p~n", [prime_factors(111)]).
+
diff --git a/test/mobius_test.erl b/test/mobius_test.erl
new file mode 100644
index 0000000..0f54d66
--- /dev/null
+++ b/test/mobius_test.erl
@@ -0,0 +1,24 @@
+%%%-------------------------------------------------------------------
+%%% @author ivan-igorevich
+%%% @copyright (C) 2023, self
+%%% @doc
+%%%
+%%% @end
+%%% Created : 13. Feb 2023 9:03 AM
+%%%-------------------------------------------------------------------
+-module(mobius_test).
+-include_lib("eunit/include/eunit.hrl").
+
+mobius_test_() -> [
+  {"Test is_prime", fun test_is_prime/0}
+].
+
+test_is_prime() ->
+  ?assertNot(mobius:is_prime(1)),
+  ?assert(mobius:is_prime(2)),
+  ?assert(mobius:is_prime(3)),
+  ?assertNot(mobius:is_prime(58)),
+  ?assert(mobius:is_prime(59)),
+  ?assertNot(mobius:is_prime(60)),
+  ?assertNot(mobius:is_prime(112)),
+  ?assert(mobius:is_prime(113)).