カテゴリー: Go Lang

package main

import (
	"fmt"
)

type person struct {
	FirstName	string
	FamilyName	string
	Age			int8
}

type inf interface{
	print()
	exchange()
}

func (p *person) print(){
	fmt.Println(p.FirstName, p.FamilyName, p.Age)
}

func (p *person) exchange(){
	fn := p.FirstName
	p.FirstName = p.FamilyName
	p.FamilyName = fn
	p.print()
}

func main(){
	var i1 inf = &person{
		FirstName: "Mary",
		FamilyName: "Bloody",
		Age: 36,
	}

	i1.print()

	i1.exchange()
}

Mary Bloody 36
Bloody Mary 36

package main

import (
	"fmt"
)

type Person struct{
	LastName string
	FirstName string
	Age int
}

func (p Person) printPerson(p1 *Person) Person{
	p1.Age = 72
	fmt.Println("John : ", p1.FirstName, p1.LastName, p1.Age)
	return *p1
}

func main() {
	var john Person
	john.FirstName = "John"
	john.LastName = "Wein"
	john .Age = 70
	john.printPerson(&john)
	fmt.Println("returned age : ", john.Age)
}

以下はポインタ渡しと値渡しでの実行結果です、確かに値渡しではオリジナルの情報は更新されません。

<ポインター渡し>
John :  John Wein 72
returned age :  72

<値渡し>
John : John Wein 72
returned age : 70

package main

import "fmt"

func main() {
	val := 20
	pointer := &val
	*pointer = 23
	fmt.Println("address : ", pointer, "value : ", val)
}


address :  0x14000126008 value :  23

package main

import (
    "sync"
	"time"
	"fmt"
)

//
// to use channel instead of "WaitGroup"
//
// in this case, slower than WaitGroup. Channel may be useful when it takes long processing time and less inforamtion size
//
func main() {
	maxNumber := 1000*10000
	var mu sync.Mutex
	ch := make(chan int)
	defer close(ch)
	c := 2
	oddCh := []int{}
	tStart := time.Now()
	tStop := time.Now()
	for i := 2; i <= maxNumber; i++ {
		go func() {
			flag := true		// if odd number, stay "true"
			mu.Lock()
			defer mu.Unlock()
			for j :=2; j*j <= c ; j++ {
				if c%j == 0{
					flag = false
					break
				}
			}
			if flag == true{
				ch <- c
			}			
			c++
		}()
	}
	for i:= 0; i < maxNumber; i++{				// set odd numbers to the slice
		setBreak := false
		select {
		case p := <- ch:
			oddCh = append(oddCh, p)
			tStop = time.Now()
		case <- time.After(time.Second):		// to check last "ch" data
			fmt.Println("Time Out!")
			setBreak = true
		}
		if setBreak == true{
			break
		}
	}
	
	fmt.Println("len : ", len(oddCh))

	el := tStop.Sub(tStart)
	fmt.Println(el)
}

package main
import "fmt"
func main(){
	fmt.Println("hello Go")
}

% mkdir mod
% cd mod
% go mod init mod 
% cp ../hello_go.go ./
% go mod tidy
% go build
% ./mod
hello Go

$ wget https://go.dev/dl/go1.19.4.linux-armv6l.tar.gz

$ sudo tar -C /usr/local -xzf go1.19.4.linux-armv6l.tar.gz

/usr/local/go/bin/に移動して、

$ ./go version
go version go1.19.4 linux/arm

まだパスが通っていない、

パスを通す、

$ echo 'export PATH=$PATH:/usr/local/go/bin' >> ~/.bashrc
$ echo 'export PATH=$HOME/go/bin:$PATH' >> ~/.bashrc

$ source ~/.bashrc

package main

import "fmt"

func main() {
    fmt.Println("Hello world")
}

$ tree ../go_prj
../go_prj
├── go.mod
├── main
└── main.go