Go

🐱‍💻 Go Numeric Types (bits) - https://golang.org/ref/spec 🐱‍💻 Go Standard Library (bits) - https://golang.org/pkg/

Print

 // Println, Printf, Print, Sprintf
package main

import "fmt"

func main() {
    name := "amy"
    age := 18
    fmt.Print("hello, ")
    fmt.Println("world!")
    fmt.Print("amy! \n")
    fmt.Print("my name is ", name)
    fmt.Println("my age is ", age)

    fmt.Printf("my name is %v and my age is %v \n", name, age)
    fmt.Printf("my name is %q and my age is %v \n", name, age)
    fmt.Printf("age is of type %T \n", age)
    fmt.Printf("you scored %f points \n", 7.19)
    fmt.Printf("you scored %0.1f points \n", 7.19)

    var str = fmt.Sprintf("my name is %v and my age is %v \n", name, age)
    fmt.Printf("the saved string is: %v", str)
}

array

 // array slice & append
package main

import "fmt"

func main() {
    names := []string{"amy", "Shieh", "aliveAmy"}
    fmt.Println(names, len(names))
    names = append(names, "changqing")
    fmt.Println(names, len(names))

    startNames := names[:3]
    fmt.Println(names, len(names), startNames, len(startNames))

    endNames := names[1:]
    fmt.Println(endNames)

    middleNames := names[0:2]
    fmt.Println(middleNames)
}

sort & strings lib

package main

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

func main() {
    greeting := "hello there~"
    //Contains
    fmt.Println(strings.Contains(greeting, "he"))
    //ReplaceAll
    fmt.Println(strings.ReplaceAll(greeting, "hello", "Hi!"))
    //ToUpper
    fmt.Println(strings.ToUpper("amy"))
    //Index
    fmt.Println(strings.Index("aliveAmy", "a"))
    //Split
    fmt.Println(strings.Split("aliveAmy", "a"))

    ages := []int{7,19,3,4,5,6}
    //Sort.Int
    sort.Ints(ages)
    fmt.Println(ages)
    //Sort.SearchInts
    fmt.Println(sort.SearchInts(ages, 19))

    names := []string{"xie", "chang", "qing", "alive", "amy"}
    //Sort.Strings
    sort.Strings(names)
    fmt.Println(names)
    //Sort.SearchStrings
    fmt.Println(sort.SearchStrings(names, "amy"))
}

for 循环【index,value】

names := []string{"xie", "chang", "qing", "alive", "amy", "aliveAmy"}

while

i := 0
for i < 7 {
    fmt.Printf("Value of x is %v", i);
    i++
}

for

for i := 0; i < 7; i++ {
    fmt.Printf("i is %v", i)
}

range (for of)

for index, value := range names {
    fmt.Printf("the index %v of name %v is", index, name)
}

for _, value := range names {
fmt.Printf("the name %v is", name)
}

note

for _, value := range name {
    value = "new name"
}

fmt.Println(names)  //[xie chang qing alive amy aliveAmy]

It does not change the original value

condition for loop

names := []string{"xie", "chang", "qing", "alive", "amy", "aliveAmy"}

    for index, name := range names {
        if index == 0 {
            fmt.Println("ignore it")
            continue
        }

        if index == (len(names) - 1) {
            fmt.Printf("%v is the last one\n", name)
            break
        }

        fmt.Printf("the pos %v of name %v is \n", index, name)

    }

function call

package main
import (
    "fmt"
    "math"
)

func greeting(p string) {
    fmt.Printf("Good morning %v ! \n", p)
}

func greeting2EveryOne(names []string, f func(name string)) {
    for _, name := range names {
        f(name)
    }
}

func calculateCircleArea(r float64) float64 {
    return math.Pi * r * r
}


func main() {
    names := []string{"xie", "chang", "qing", "alive", "amy", "aliveAmy"}
    greeting( "amy")
    greeting2EveryOne(names, greeting)
    circle1 := calculateCircleArea(2.5)
    circle2 := calculateCircleArea(5)

    fmt.Printf("circle1's area is %0.1f, circle2's area is %0.3f",  circle1, circle2)
}

multiple value return

package main

import (
    "fmt"
    "strings"
)

//go中函数返回多个值就是这样的写法，那假如参数很多的时候，有没有更好地写法呢？
func getMultipleName(n string) (string, string) {
    names := strings.Split(n, " ")
    if len(names) > 1 {
        // 感觉有点像js中数组、对象解构赋值的写法呢~
        return names[0], names[1]
    }
    return names[0], "_"
}

func main()  {
    firstName, lastName := getMultipleName("alive Amy")
    firstName1, lastName1 := getMultipleName("alive")
    fmt.Println(firstName, lastName)
    fmt.Println(firstName1, lastName1)
}

package ref

parent.go

package main
import "fmt"
var hobbies = []string{"reading", "painting"}
func main() {
    sayHello("amy")
    for _, value := range getNamesFromChild {
        fmt.Println(value)
    }
    getValueFromParent()
}

child.go

package main
import "fmt"

var getNamesFromChild = []string{"xie", "chang", "qing", "alive", "amy", "aliveAmy"}

func sayHello(name string)  {
    fmt.Printf("hello, %v", name)
}
func getValueFromParent() {
    for _, value := range hobbies{
        fmt.Println(value)
    }
}

package call shell

go run parent.go child.go

Map【key, value】

package main
import "fmt"

func main() {
    names := map[int]string {
        0: "amy",
        1: "aliveAmy",
        2: "changqing",
        3: "amyShieh",
    }

    for key, value := range names {
        fmt.Println(key, "-", value)
    }
}

passing value

"引用类型"的存储：堆栈, address => stack, value => heap reference "基本类型"的存储: stack， copies

basic	reference
Strings Ints floats Booleans Arrary	Slices Maps Functions

pointer

package main

import "fmt"

func updateName(n *string)  {
    *n = "aliveAmy"
}

func main()  {
    name := "amy"
    position := &name
    fmt.Println("original name", name)
    updateName(position)
    fmt.Println("changed name", name)
}

Custom type & struct

bill.go

package main

type bill struct {
    name string
    items map[string] float64
    tips float64
}

func newBill(name string) bill {
    myBill := bill{
        name: name,
        items: map[string]float64 {},
        tips: 0,
    }
    return myBill
}

mian.go

package main

import "fmt"

func main()  {
    fmt.Println(newBill("amy's bill"))
}

go run main.go bill.go