little-go-book

README.md

little-go-book

1. Basics

go version
# go version go1.21.5 darwin/arm64

godoc -http=:6060

go run main.go
# it's over 9000!

go run --work main.go
# WORK=/var/folders/y1/jbmj09k53xs164wgqc3mxl080000gp/T/go-build4184586122
# it's over 9000!

go build main.go
./main
# it's over 9000!

go run main1.go
# exit status 1

go run main1.go 9001
# It's over 9001

go run main2.go
# Goku's power is over 9000

2. Structures

go run main4.go
# 9000
# 19000

go run main5.go
# 19001

go run main7.go
# Hi, I am Goku

go run main8.go
# Hi, I'm Goku. Ya!
# Hi, I am Goku

3. Maps, Arrays, Slices

go run main9.go
# 0= 9001
# 1= 9333
# 2= 212
# 3= 33

go run main10.go
## command-line-arguments
#./main10.go:4:2: names declared and not used
#./main10.go:5:2: checks declared and not used
#./main10.go:6:6: names redeclared in this block
#        ./main10.go:4:2: other declaration of names
#./main10.go:7:2: scores declared and not used

main.go

package main

func main() {
	println("it's over 9000!")
}

main1.go

package main

import (
	"fmt"
	"os"
)

func main() {
	if len(os.Args) != 2 {
		os.Exit(1)
	}
	fmt.Println("It's over", os.Args[1])
}

main10.go

package main

func main() {
	names := []string{"leto", "jessica", "paul"}
	checks := make([]bool, 10)
	var names []string
	scores := make([]int, 0, 20)
}

main2.go

package main

import (
	"fmt"
)

func main() {
	name, power := "Goku", 9000
	fmt.Printf("%s's power is over %d\n", name, power)
}

main3.go

package main

import (
	"fmt"
)

type Saiyan struct {
	Name  string
	Power int
}

func main() {
	goku := Saiyan{Name: "Goku"}
	goku.Power = 9000
	fmt.Printf("%s is %d\n", goku.Name, goku.Power)
}

main4.go

package main

import (
	"fmt"
)

type Saiyan struct {
	Name  string
	Power int
}

func main() {
	// CHANGES NOT REFLECTED!
	goku := Saiyan{"Goku", 9000}
	Super(goku)
	fmt.Println(goku.Power)

	// USE ADDRESS OF OPERATOR
	gokuA := &Saiyan{"Goku", 9000}
	SuperA(gokuA)
	fmt.Println(gokuA.Power)
}

func Super(s Saiyan) {
	s.Power += 10000
}

func SuperA(s *Saiyan) {
	s.Power += 10000
}

main5.go

package main

import (
	"fmt"
)

type Saiyan struct {
	Name  string
	Power int
}

func (s *Saiyan) Super() {
	s.Power += 10000
}

func main() {
	goku := &Saiyan{"Goku", 9001}
	goku.Super()
	fmt.Println(goku.Power)
}

main6.go

package main

import (
	"fmt"
)

type Saiyan struct {
	Name  string
	Power int
}

func (s *Saiyan) Super() {
	s.Power += 10000
}

func NewSaiyan(name string, power int) *Saiyan {
	return &Saiyan{
		Name:  name,
		Power: power,
	}
}

func main() {
	goku := NewSaiyan("Goku", 9001)
	goku.Super()
	fmt.Println(goku.Power)
}

main7.go

package main

import (
	"fmt"
)

type Person struct {
	Name string
}

func (p *Person) Introduce() {
	fmt.Printf("Hi, I am %s\n", p.Name)
}

type Saiyan struct {
	*Person
	Power int
}

func main() {
	goku := &Saiyan{
		Person: &Person{"Goku"},
		Power: 9001,
	}
	goku.Introduce()

	// These are the same:
	fmt.Println(goku.Name)
	fmt.Println(goku.Person.Name)
}

main8.go

package main

import (
	"fmt"
)

type Person struct {
	Name string
}

func (p *Person) Introduce() {
	fmt.Printf("Hi, I am %s\n", p.Name)
}

type Saiyan struct {
	*Person
	Power int
}

func (s *Saiyan) Introduce() {
	fmt.Printf("Hi, I'm %s. Ya!\n", s.Name)
}

func main() {
	goku := &Saiyan{
		Person: &Person{"Goku"},
		Power: 9001,
	}
	goku.Introduce()

	goku.Person.Introduce()
}

main9.go

package main
import ("fmt")

func main() {
	scores := [4]int{9001, 9333, 212, 33}
	for index, value := range scores {
		fmt.Printf("%d= %d\n", index, value)
	}
}