Add Euler totient

Author: PraneethJain

.spec/math/totient_spec.lua

@@ -0,0 +1,22 @@
+describe("Totient", function()
+	local totient = require("math.totient")
+	it("should handle edge cases", function()
+		assert.equal(1, totient(1))
+	end)
+
+	it("totient of prime p should be p - 1", function()
+		assert.equal(1, totient(2))
+		assert.equal(2, totient(3))
+		assert.equal(4, totient(5))
+		assert.equal(78, totient(79))
+		assert.equal(96, totient(97))
+	end)
+
+	it("should handle general cases", function()
+		assert.equal(2, totient(4))
+		assert.equal(12, totient(42))
+		assert.equal(36, totient(63))
+		assert.equal(24, totient(72))
+		assert.equal(40, totient(100))
+	end)
+end)

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2023 Lars Müller
+Copyright (c) 2023 Lars Müller and contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

src/math/totient.lua

@@ -0,0 +1,13 @@
+local gcd = require("math.greatest_common_divisor")
+
+return function(
+	n -- number
+)
+	local totient = 0
+	for i = 1, n do
+		if gcd(i, n) == 1 then -- relatively prime?
+			totient = totient + 1
+		end
+	end
+	return totient -- number of positive integers less than n that are relatively prime to n
+end