mathtools/cmd/totient.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 (
	"bufio"
	"fmt"
	"os"

	"github.com/spf13/cobra"
	"scm.dairydemon.net/filifa/mathtools/internal/lib/sieve"
)

var totientN uint

func totient(cmd *cobra.Command, args []string) {
	bufStdout := bufio.NewWriter(os.Stdout)
	defer bufStdout.Flush()

	for v := range sieve.Totient(totientN, 1000) {
		if v == 0 {
			continue
		}

		fmt.Fprintln(bufStdout, v)
	}
}

// totientCmd represents the totient command
var totientCmd = &cobra.Command{
	Use:   "totient -n N",
	Short: "Compute the totient function for all numbers less than n",
	Long: `Compute the totient function for all numbers less than n.

The totient function phi(n) counts the numbers up to n that are coprime to n.`,
	Run: totient,
}

func init() {
	sieveCmd.AddCommand(totientCmd)

	// Here you will define your flags and configuration settings.

	// Cobra supports Persistent Flags which will work for this command
	// and all subcommands, e.g.:
	// totientCmd.PersistentFlags().String("foo", "", "A help for foo")

	// Cobra supports local flags which will only run when this command
	// is called directly, e.g.:
	// totientCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")

	totientCmd.Flags().UintVarP(&totientN, "limit", "n", 0, "upper limit")
	totientCmd.MarkFlagRequired("limit")
}