Go language introduction detailed knowledge, mainly to share with you go language composition, go language function format, C language to go language comparison.

Go language program composition

• Like C language program, Go language program is also composed of many functions

• Like C language programs, the system * automatically calls a function called main when the program runs

• Like C language programs, if a program does not have a main function, the program does not have the ability to run

• Like C language programs, a Go language program has and can only have one main function

Go language program main function definition format

• C language main function format

int main(int argc, const char * argv[]) {
    return 0;
}

• Go language main function format

  • func tells the system that this is a function

  • Main main function fixed name

  • The left parenthesis of a function must be on the same line as the function name

  • The main function must be in the main package

//Tell the system which package the currently written code belongs to
package main
//Defines a function called main
func main() {
}

Go language HelloWorld

package main //Tell the system that the current code belongs to the main package
import "fmt" //Import fmt package corresponding to print function
func main() {
        //By package name Function name, using the print function in fmt package to output statements
 fmt.Println("Hello World!!!")
}

Similarities and differences between Go language HelloWorld and C language HelloWorld

• 1. Different file types

  • c language code is saved in c is the suffix of the file

  • The go language code is saved in In files with go suffix

• 2. Different code management methods

  • We will put different types of code into different go file, and then assign a package name to the file through package

  • If necessary, you can directly import the corresponding package name through import

    

  • c language will put different types of code into different c file, and then write the corresponding h file

  • If necessary, import the corresponding files directly through #include h file is enough

    

  • C language programs manage code in the form of files

  • Go language program manages code in the form of package

• 3. The main function writing file is different

• The main function in C language can be written in any file, as long as a program has only one main function

• In Go language, the main function can only be written in the folder named main in the package. Similarly, a program needs to be saved, and there is only one main function

• 4. Functions are written in different formats

  • Note: the left bracket of C language function can be on the same line as the function name or not

  • The format of function in C language is

return type Function name(parameter list ) {
        Function body related statements;
        return Return value;
}

• • Note: the left bracket of Go language function must be on the same line as the function name, otherwise an error will be reported

  • Go language function definition format

func  Function name(parameter list )(Return value list) {
        Function body related statements;
        return Return value;
}

• 5. The format of function call is different

  • C language is imported through #include h file, call the function directly through the function name

  • After the Go language imports the corresponding package through import, it needs to pass the package name Called by function name

#include <stdio.h>
#include "calculate.h"
int main()
{
    int res = sum(2, 3); //Call the function directly with the function name
    printf("res = %d!\n", res);
    return 0;
}

package main
import (
 "fmt"
 "lesson_1/calculate"
)
func main() {
 res := calculate.Sum(2, 3) //Use package name Function name calling function
 fmt.Println("res1 = ", res)
}

• 6. The statement ends differently

  • Every statement in C language must end with a semicolon

  • There is no need to add a semicolon after each statement in Go language (the compiler will add it automatically)

#include <stdio.h>
#include "calculate.h"
int main()
{
    int res = sum(2, 3); //If you don't write a semicolon, you will report an error
    printf("res = %d!\n", res); //If you don't write a semicolon, you will report an error
    return 0; //If you don't write a semicolon, you will report an error
}

package main
import (
 "fmt"
 "lesson_1/calculate"
)
func main() {
 res := calculate.Sum(2, 3) //Don't write semicolons
 fmt.Println("res1 = ", res) //Don't write semicolons
}

Go language notes

• Like C language, Go language also supports single line comments and multi line comments, and the characteristics of all comments are the same as C language

  • Single line comment / / annotated content

  • Multiline comment / * annotated content*/

• In the Go language, the official recommends using single line comments rather than multi line comments (for details, you can directly view the official Go source code)