Go Language Basics · ThinkerQAQ

This is a historical learning note and may contain outdated or incomplete understanding.

1. Keywords

1.1. for

1.1.1. Different Forms of the for Loop

1.1.1.1. Classic for Loop

//for (init;before;after)
sum := 0
for i := 0; i < 10; i++ {
	sum += i
}

1.1.1.2. while Loop

//while(xxx)
x := 0
for x < 100 {
	fmt.Println(x)
	x = x + 1
}

1.1.1.3. Infinite Loop

//for(;;)
for {
	fmt.Println("test")
}

1.1.1.4. Enhanced for Loop


//	Iterate over arrays, slices, strings, or maps, or receive messages from a channel
oldMap := map[int]string{
	1: "a",
	2: "b",
}

newMap := make(map[int]string)
for k, v := range oldMap {
	newMap[k] = v
}

Note: the enhanced for loop iterates using the same address, which can cause problems under concurrency.

func TestFor(t *testing.T) {
	arrays := []uint64{1,2,4}

	for _, val := range arrays {
		fmt.Println(&val, val)
	}

}

// Output

0xc00000a310 1
0xc00000a310 2
0xc00000a310 4

Solution: use a local variable.

func TestFor(t *testing.T) {
	arrays := []uint64{1,2,4}

	for _, val := range arrays {
		tmpVal := val
		fmt.Println(&tmpVal, tmpVal)
	}

}

// Output
0xc00000a310 1
0xc00000a320 2
0xc00000a330 4

1.2. switch

func unhex(c byte) {
	//switch {
	//case c >= '0':
	//	fmt.Println("c>=0")
	//case c == '0':
	//	fmt.Println("c==0")
	//default:
	//	fmt.Println("c<0")
	//}

	switch c {
	case '0':
		fmt.Println("0")
	case '1', '2':
		fmt.Println("1")
		break // adding break manually is also OK; qqqqq below will not be printed
		fmt.Println("qqqqqqqqqqqqqq")
	default:
		fmt.Println("others")
	}

}