Go - Advanced Go Features - Finding the number of occurrences、threshold、stringsパッケージ、Fields関数、コマンドライン引数、osパッケージ、Argsスライス

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 3(Advanced Go Features)、Exercises 12.の解答を求めてみる。

コード

package main

import (
 "fmt"
 "os"
 "strconv"
 "strings"
)

func main() {
 threshold := 0
 if len(os.Args) > 1 {
  if n, err := strconv.Atoi(os.Args[1]); err != nil {
   fmt.Println("Usage: occurences [threshold]")
  } else {
   threshold = n
  }
 }
 strs := []string{
  "1 b 3 1 a a b",
  "11 a 1 1 1 1 a a",
  "-1 b 1 -4 a 1",
 }
 counts := map[string]int{}
 for _, s := range strs {
  for _, word := range strings.Fields(s) {
   counts[word]++
  }
 }
 for k, v := range counts {
  if v > threshold {
   fmt.Printf("%v -> %v\n", k, v)
  }
 }
}

入出力結果(Zsh、PowerShell、Terminal)

% go build 
% ./occurrences 
1 -> 8
b -> 3
3 -> 1
a -> 6
11 -> 1
-1 -> 1
-4 -> 1
% ./occurrences 0
11 -> 1
-1 -> 1
-4 -> 1
1 -> 8
b -> 3
3 -> 1
a -> 6
% ./occurrences 1
1 -> 8
b -> 3
a -> 6
% ./occurrences 2
1 -> 8
b -> 3
a -> 6
% ./occurrences 3
1 -> 8
a -> 6
% ./occurrences 4
1 -> 8
a -> 6
% ./occurrences 5
1 -> 8
a -> 6
% ./occurrences 6
1 -> 8
% ./occurrences 7
1 -> 8
% ./occurrences 8 
% ./occurrences a
Usage: occurrences [threshold]
1 -> 8
b -> 3
3 -> 1
a -> 6
11 -> 1
-1 -> 1
-4 -> 1
%