Go language chapter 2 (for loop)
Summary : There is no while loop construct in Go language. However, similar functionality can be achieved with for loops and break statements.
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for
In the Go language, a for loop is a construct used to repeatedly execute a block of code. Its basic syntax is as follows:
for 初始化语句; 条件表达式; 后置语句 {
// 循环体
}
Among them, the initialization statement is executed before the first loop, usually used to initialize variables; the conditional expression is evaluated before each loop, if it is true, then continue to execute the loop body, otherwise jump out of the loop; the post statement is executed in each loop After execution, it is usually used to update variables.
For example, the following code uses a for loop to calculate the sum from 1 to 10:
sum := 0
for i := 1; i <= 10; i++ {
sum += i
}
fmt.Println(sum) // 输出 55
In this example, the initialization statement is i := 1to initialize the variable i to 1; the conditional expression is i <= 10to continue executing the loop body as long as i is not greater than 10; the postfix statement is i++to add 1 to i after each loop.
The for loop in Go language can have many variants, for example:
- The initialization statement and the post statement can be omitted, and only the conditional expression is reserved to realize the function of the while loop.
i := 0
for i < 10 {
fmt.Println(i)
i++
}
- All statements can be omitted to realize the function of infinite loop.
for {
fmt.Println("无限循环")
}
- You can use the range keyword to traverse collection types such as arrays, slices, and maps.
arr := []int{
1, 2, 3}
for index, value := range arr {
fmt.Printf("索引：%d，值：%d\n", index, value)
}
In addition to the above commonly used forms, the for loop of Go language also supports label syntax and continue/break/return statements, which can realize more complex control flow structures. It should be noted that when writing a loop, pay attention to the correctness of the loop condition expression and avoid the occurrence of an infinite loop.
example
1. Print the numbers from 1 to 10
package main
import "fmt"
func main() {
for i := 1; i <= 10; i++ {
fmt.Println(i)
}
}
2. Calculate the sum from 1 to 100
package main
import "fmt"
func main() {
sum := 0
for i := 1; i <= 100; i++ {
sum += i
}
fmt.Println("1到100的和为：", sum)
}
3. Print the ninety-nine multiplication table
package main
import "fmt"
func main() {
for i := 1; i <= 9; i++ {
for j := 1; j <= i; j++ {
fmt.Printf("%d*%d=%d ", j, i, i*j)
}
fmt.Println()
}
}
4. Using a for loop to iterate through an array
package main
import "fmt"
func main() {
arr := []int{
1, 2, 3}
for i := 0; i < len(arr); i++ {
fmt.Printf("索引：%d，值：%d\n", i, arr[i])
}
}