/* hello.go */

package main

import (

	"fmt"

)

func main() {

	a, b := 12, 20

	var c int

	c = a + b //32

	c = a - b //-8

	c = a * b //240

	c = a / b //0 地板除，只取整数部分

	c = b / a //1 地板除，只取整数部分，

	c = a % b //12

	c = b % a //8

	fmt.Println("c =", c)

	//c = a++ 自增和自减不能作为赋值表达式

	//++a 不能这样写，自增、自减符号只能跟变量后

	a++

	fmt.Println("a =", a)

	b--

	fmt.Println("b =", b)

}

/* hello.go */

package main

import (

	"fmt"

)

func main() {

	a, b := 12, 20

	fmt.Println("数字比较")

	fmt.Println(a == b) //false

	fmt.Println(a != b) //true

	fmt.Println(a > b)  //false

	fmt.Println(a < b)  //true

	fmt.Println(a >= b) //false

	fmt.Println(a <= b) //true

	c, d := "Jalen", "Jalen"

	fmt.Println("字符串比较")

	fmt.Println(c == d) //true

	e, f := "Jalen1", "Jalen2"

	fmt.Println(e == f) //false

	fmt.Println(e > f)  //false

	fmt.Println(e < f)  //true

	g, h := "abc_a", "abc_b"

	fmt.Println(g > h) //false

	fmt.Println(g < h) //true

}

/* hello.go */

package main

import (

	"fmt"

)

func main() {

	a, b := true, false

	fmt.Println(a && b) //false

	fmt.Println(a || b) //true

	fmt.Println(!a)     //false

	fmt.Println(!b)     //true

	// 下面报 invalid operation: m && n (operator x not defined on int)

	// m, n := 0, 1

	// fmt.Println(m && n) //false

	// fmt.Println(m || n) //true

	// fmt.Println(!m)     //false

	// fmt.Println(!n)     //true

}

/* hello.go */

package main

import (

	"fmt"

)

func main() {

	var a int = 50     // 对应二进制：0011 0010

	var b int = 60     // 对应二进制：0011 1100

	fmt.Println(a & b) //48，对应二进制：0011 0000

	fmt.Println(a | b) //62，对应二进制：0011 1110

	fmt.Println(a ^ b) //14，对应二进制：0000 1110

	fmt.Println(a << 2) //200，二进制左移 2 位，相当于 *2^2 对应二进制：1100 1000

	fmt.Println(b >> 2) //15，二进制右移 2 位，相当于 /2^2 对应二进制：0000 1111

}

/* hello.go */

package main

import (

	"fmt"

)

func main() {

	var a int = 12

	var b int = 20

	var c int

	c = a + b //32

	c += a    //44

	c -= a    //32

	c *= a    //384

	c /= a    //32

	c %= a    //8

	c <<= a   //32768

	c >>= a   //8

	c &= a    //1000 & 1100 = 1000 = 8

	c ^= a    //1000 ^ 1100 = 1100 = 4

	c |= a    //0100 | 1100 = 1100 = 12

	fmt.Println(c)

}

/* hello.go */

package main

import (

	"fmt"

)

func main() {

	var a int = 4

	var b int32

	var c float32

	var ptr *int // 声明 ptr 为指针变量

	fmt.Printf("第 1 行 - a 变量类型为 = %T\n", a)

	fmt.Printf("第 2 行 - b 变量类型为 = %T\n", b)

	fmt.Printf("第 3 行 - c 变量类型为 = %T\n", c)

	// 直接用变量赋值报：cannot use a (variable of type int) as *int value in assignment

	// ptr = a

	ptr = &a                        // 必须添加 & amp; 符号，表示返回变量存储地址

	fmt.Printf("a 的值为  %d\n", a)    //4

	fmt.Printf("*ptr 为 %d\n", *ptr) //4

	fmt.Printf("ptr 为 %d\n", ptr)   //824633794696

	// 使用指针与不使用指针的区别

	var num1 = 12

	var ptr1 int

	ptr1 = num1

	fmt.Println(ptr1) //12

	num1 = 20

	fmt.Println(ptr1) //12

	var num2 = 12

	var ptr2 *int

	ptr2 = &num2

	fmt.Println(*ptr2) //12

	num2 = 20

	fmt.Println(*ptr2) //20

}