104 lines
2.4 KiB
Go
104 lines
2.4 KiB
Go
/*
|
|
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 cmd
|
|
|
|
import (
|
|
"fmt"
|
|
|
|
"github.com/spf13/cobra"
|
|
)
|
|
|
|
var mobiusN uint
|
|
|
|
func mobiusSieve(n uint) chan int {
|
|
sieve := make([]int, n)
|
|
for i := 0; i < int(n); i++ {
|
|
sieve[i] = i
|
|
}
|
|
|
|
ch := make(chan int)
|
|
go func() {
|
|
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
|
|
}
|
|
}
|
|
|
|
close(ch)
|
|
}()
|
|
|
|
return ch
|
|
}
|
|
|
|
func mobius(cmd *cobra.Command, args []string) {
|
|
ch := mobiusSieve(mobiusN)
|
|
for i := 0; ; i++ {
|
|
v, ok := <-ch
|
|
if !ok {
|
|
break
|
|
}
|
|
|
|
if i == 0 {
|
|
continue
|
|
}
|
|
|
|
fmt.Println(v)
|
|
}
|
|
}
|
|
|
|
// mobiusCmd represents the mobius command
|
|
var mobiusCmd = &cobra.Command{
|
|
Use: "mobius -n N",
|
|
Short: "Compute the Möbius function for all numbers less than n",
|
|
Long: `Compute the Möbius function for all numbers less than n.
|
|
|
|
The Möbius function mu(n) is a multiplicative function defined as follows for prime p:
|
|
mu(p) = -1
|
|
mu(p^k) = 0 for k > 1
|
|
|
|
This means for squarefree n, mu(n) = -1 if n has an odd number of prime factors and mu(n) = 1 if n has an even number of prime factors. mu(n) = 0 if n is not squarefree.`,
|
|
Run: mobius,
|
|
}
|
|
|
|
func init() {
|
|
sieveCmd.AddCommand(mobiusCmd)
|
|
|
|
// Here you will define your flags and configuration settings.
|
|
|
|
// Cobra supports Persistent Flags which will work for this command
|
|
// and all subcommands, e.g.:
|
|
// mobiusCmd.PersistentFlags().String("foo", "", "A help for foo")
|
|
|
|
// Cobra supports local flags which will only run when this command
|
|
// is called directly, e.g.:
|
|
// mobiusCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
|
|
|
|
mobiusCmd.Flags().UintVarP(&mobiusN, "limit", "n", 0, "upper limit")
|
|
mobiusCmd.MarkFlagRequired("limit")
|
|
}
|