Go - Writing Programs in Go - 簡単な乱数生成器

Go Systems Programming:
Master Linux and Unix
system level programming with Go
楽天ブックス 紀伊國屋書店

開発環境

• macOS Catalina - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Go (プログラミング言語)

Go Systems Programming: Master Linux and Unix system level programming with Go (Mihalis Tsoukalos(著)、Packt Publishing)のChapter 2(Writing Programs in Go)、Exercises 7.の解答を求めてみる。

コード

package main

import (
 "fmt"
 "os"
 "strconv"
 "time"
)

func errPrintln(err error) {
 if err != nil {
  fmt.Fprintln(os.Stderr, err)
  os.Exit(1)
 }
}

var seedN int

func seed(n int64) {
 seedN = int(n)
}
func intn(n int) int {
 if n <= 0 {
  panic("intn(n int) n <= 0")
 }
 m := seedN % n
 seedN = seedN*seedN + 1
 if seedN < 0 {
  seedN *= -1
 }
 return m
}
func random(min, max int) int {
 return intn(max-min) + min
}
func main() {
 MIN := 0
 MAX := 0
 TOTAL := 0
 if len(os.Args) > 3 {
  var err error
  MIN, err = strconv.Atoi(os.Args[1])
  errPrintln(err)
  MAX, err = strconv.Atoi(os.Args[2])
  errPrintln(err)
  TOTAL, err = strconv.Atoi(os.Args[3])
  errPrintln(err)
 } else {
  errPrintln(fmt.Errorf("Usage: %v MIX MAX TOTAL", os.Args[0]))
 }
 if MIN < 0 || MIN >= MAX {
  errPrintln(fmt.Errorf("MIN >= 0 and MIN < MAX"))
 }
 seed(time.Now().UnixNano())
 for i := 0; i < TOTAL; i++ {
  myrand := random(MIN, MAX)
  fmt.Print(myrand)
  fmt.Print(" ")
 }
 fmt.Println()
}

入出力結果(Zsh、PowerShell、Terminal)

% ./random       
Usage: ./random MIX MAX TOTAL
% ./random 0 a 10
strconv.Atoi: parsing "a": invalid syntax
% ./random 0 0 10
MIN >= 0 and MIN < MAX
% ./random 0 1 10
0 0 0 0 0 0 0 0 0 0 
% ./random 0 2 10
0 1 0 1 0 1 0 1 0 1 
% ./random 0 2 10
0 1 0 1 0 1 0 1 0 1 
% ./random 0 2 10
0 1 0 1 0 1 0 1 0 1 
% ./random 0 3 10
2 0 1 1 0 2 0 1 1 1 
% ./random 0 3 10
1 0 2 1 1 1 2 0 0 0 
% ./random 0 3 10
1 2 1 2 1 2 1 0 2 2 
% ./random 0 3 10
0 1 2 0 0 1 2 2 1 0 
% ./random 0 4 10
0 3 2 3 2 1 2 1 2 3 
% ./random 5 10 10
5 8 6 7 7 5 8 5 9 8 
% ./random 5 10 10
5 6 7 5 7 9 9 8 5 8 
% ./random 95 105 10
95 96 99 98 99 102 95 102 103 104 
% ./random 95 105 10
95 98 97 102 99 98 103 98 95 98 
% ./random 95 105 10
95 102 95 100 103 98 99 96 95 104 
% ./random 95 105 10
95 96 99 96 103 96 101 104 97 98 
% ./random 95 105 10
95 96 103 104 103 102 103 100 97 96 
%