What are the ways to write for in go language?

There are three ways to write the For loop in Go language: 1. The same way of writing as C language for, with the syntax "for init; condition; post {...}"; 2. The same way of writing as C language while , the syntax is "for condition {...}"; 3. The same writing method as C language for(;;), the syntax is "for {...}". It should be noted that the left curly bracket "{" must be on the same line as the for keyword.

The operating environment of this tutorial: Windows 7 system, GO version 1.18, Dell G3 computer.

Different from most languages, the loop statement in the Go language only supports the for keyword and does not support the while and do-while structures.

The for loop is a loop control structure that can execute a specified number of loops.

How to write for loop in Go language

There are 3 forms of For loop in Go language, only one of which uses semicolon.

Same as for in C language:

for init; condition; post { }

Same as while in C:

for condition { }

Same as for(;;) in C:

for { }

• init: Generally an assignment expression, assigning an initial value to a control variable;

• condition: A relational expression or logical expression, a loop control condition;

• post: Generally an assignment expression to increment or decrement the control variable.

The execution process of the for statement is as follows:

• 1. First assign an initial value to expression 1;

• 2. Determine whether the assignment expression init satisfies the given condition. If its value is true and the loop condition is met, execute the statement in the loop body, then execute post, enter the second loop, and then determine the condition; otherwise, determine the condition. If the value is false and the condition is not met, the for loop will be terminated and the statement outside the loop will be executed.

When using loop statements, you need to pay attention to the following points:

• The left curly brace { must be the same as for in the same row.

• The for loop in Go language is the same as C language, allowing variables to be defined and initialized in loop conditions. The only difference is that Go language does not support multiple comma-separated Assignment statements must use parallel assignment to initialize multiple variables.

• The for loop of Go language also supports continue and break to control the loop, but it provides a more advanced break, which can choose which loop to interrupt, as in the following example:

for j := 0; j < 5; j++ {
    for i := 0; i < 10; i++ {
        if i > 5 {
            break JLoop
        }
        fmt.Println(i)
    }
}
JLoop:
// ...

In the above code, the break statement terminates the outer loop at the JLoop label.

Usage of Go language for loop

The range format of the for loop can iterate over slices, maps, arrays, strings, etc. The format is as follows:

for key, value := range oldMap {
    newMap[key] = value
}

The key and value in the above code can be omitted.

If you only want to read the key, the format is as follows:

for key := range oldMap

Or this:

for key, _ := range oldMap

If you only want to read the value, the format is as follows:

for _, value := range oldMap

Example

Calculate the sum of numbers from 1 to 10:

package main

import "fmt"

func main() {
   sum := 0
      for i := 0; i <= 10; i++ {
         sum += i
      }
   fmt.Println(sum)
}

The output result is:

55

init and post parameters are optional, we You can omit it directly, similar to the While statement.

The following example calculates the value of sum after sum is added when sum is less than 10:

package main

import "fmt"

func main() {
   sum := 1
   for ; sum <= 10; {
      sum += sum
   }
   fmt.Println(sum)

   // 这样写也可以，更像 While 语句形式
   for sum <= 10{
      sum += sum
   }
   fmt.Println(sum)
}

The output result is:

16
16

[Related recommendations: Go video Tutorial、Programming Teaching】

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