move sieves to subpackage

internal/lib/sieve/mobius.go

@@ -0,0 +1,50 @@
+/*
+Copyright © 2025 filifa
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+package sieve
+
+/*
+MobiusSieve computes mobius(k) for k=1 to n, where mobius is the Mobius function.
+*/
+func MobiusSieve(n uint, buflen uint) chan int {
+	sieve := make([]int, n)
+	for i := 0; i < int(n); i++ {
+		sieve[i] = i
+	}
+
+	ch := make(chan int, buflen)
+	go func() {
+		defer close(ch)
+		for i := 0; i < int(n); i++ {
+			if i == 0 || i == 1 || sieve[i] != i {
+				ch <- sieve[i]
+				continue
+			}
+
+			ch <- -1
+
+			for j := 2 * i; j < int(n); j += i {
+				if j%(i*i) == 0 {
+					sieve[j] = 0
+				}
+
+				sieve[j] /= -i
+			}
+		}
+	}()
+
+	return ch
+}