Go - Go Packages, Algorithms, and Data Structures - sortパッケージ、Slice関数、引数、less関数、無名関数、関数リテラル

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 4(Go Packages, Algorithms, and Data Structures)、Exercises 2.の解答を求めてみる。

コード

package main

import (
 "fmt"
 "sort"
 "strings"
)

type person struct {
 name string
 age  int
}

func p(p1, p2 []person) {
 fmt.Println(p1)
 fmt.Println(p2)
 fmt.Println()
}
func main() {
 people := []person{
  person{name: "a", age: 5},
  person{name: "b", age: 1},
  person{name: "日本語", age: 4},
  person{name: "c", age: 2},
  person{name: "aaa", age: 3},
  person{name: "a", age: 1},
 }
 people1 := make([]person, len(people))
 copy(people1, people)
 p(people, people1)

 sort.Slice(people, func(i, j int) bool {
  return strings.Compare(people[i].name, people[j].name) == -1
 })
 p(people, people1)

 sort.Slice(people, func(i, j int) bool {
  return people[i].age < people[j].age
 })
 p(people, people1)

 sort.Slice(people1, func(i, j int) bool {
  return people1[i].age < people1[j].age
 })
 p(people, people1)

 sort.Slice(people1, func(i, j int) bool {
  return strings.Compare(people1[i].name, people1[j].name) == -1
 })
 p(people, people1)

 people = append(people, person{name: "a", age: 0})
 sort.Slice(people, func(i, j int) bool {
  switch strings.Compare(people[i].name, people[j].name) {
  case -1:
   return true
  case 1:
   return false
  default:
   return people[i].age < people[j].age
  }
 })
 fmt.Println(people)
}

入出力結果(Zsh、PowerShell、Terminal)

% go run sample2.go
[{a 5} {b 1} {日本語 4} {c 2} {aaa 3} {a 1}]
[{a 5} {b 1} {日本語 4} {c 2} {aaa 3} {a 1}]

[{a 5} {a 1} {aaa 3} {b 1} {c 2} {日本語 4}]
[{a 5} {b 1} {日本語 4} {c 2} {aaa 3} {a 1}]

[{a 1} {b 1} {c 2} {aaa 3} {日本語 4} {a 5}]
[{a 5} {b 1} {日本語 4} {c 2} {aaa 3} {a 1}]

[{a 1} {b 1} {c 2} {aaa 3} {日本語 4} {a 5}]
[{b 1} {a 1} {c 2} {aaa 3} {日本語 4} {a 5}]

[{a 1} {b 1} {c 2} {aaa 3} {日本語 4} {a 5}]
[{a 1} {a 5} {aaa 3} {b 1} {c 2} {日本語 4}]

[{a 0} {a 1} {a 5} {aaa 3} {b 1} {c 2} {日本語 4}]
%