mathtools/cmd/isprime.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"
	"log"
	"math/big"

	"github.com/spf13/cobra"
)

var rounds uint

func isprime(cmd *cobra.Command, args []string) {
	x := new(big.Int)

	primes := make([]bool, len(args))
	for i, s := range args {
		_, ok := x.SetString(s, 10)
		if !ok {
			log.Fatal("invalid input " + s)
		}

		primes[i] = x.ProbablyPrime(int(rounds))
	}

	for _, b := range primes {
		fmt.Println(b)
	}
}

// isprimeCmd represents the isprime command
var isprimeCmd = &cobra.Command{
	Use:   "isprime N [N ...]",
	Short: "Determine whether a number is prime",
	Long: `Determine whether a number is prime.

This applies 10 iterations of the Miller-Rabin test and a Baillie-PSW test. Use
flags to change the number of Miller-Rabin iterations.

For inputs less than 2^64, results are 100% accurate. For larger numbers, there
is a small chance of falsely reporting a composite number as prime. That chance
can be reduced by applying more rounds of Miller-Rabin.`,
	Args: cobra.MinimumNArgs(1),
	Run:  isprime,
}

func init() {
	rootCmd.AddCommand(isprimeCmd)

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

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

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

	isprimeCmd.Flags().UintVarP(&rounds, "rounds", "r", 10, "number of iterations of Miller-Rabin test")
}