Go language learning notes (1)

hello , world

package main

import (
	"fmt"
)

func main{
    
	fmt.Println("hello, world")
}

go The structure of language ：

• package , import, function
• Package concept and Java In the same way
• import Is equivalent to C Medium include
• The concept of function is the same as that in other languages

Requirements of braces

• go The program has mandatory requirements for the position of braces , You must write left parentheses on the same line （ When you need to write braces ）

If the above hello world The program is written as follows , Will be an error , Be careful main Brace position of function

package main

import (
	"fmt"
)

func main
{
    
	fmt.Println("hello, world")
}

although go There is no need to write a semicolon at the end of every sentence , But in fact, the compiler will add a semicolon to every sentence before compiling , If the braces are not written according to the format requirements , It will cause the compiler to be unrecognized and report syntax errors

Variable declarations

package main

import (
	"fmt"
)

func main
{
    
	const //  declare constant 
	var //  Declare variables 
	 Variable name  :=  expression  //  Declare local variables with smaller scope 
}

• When used as a function local variable , var And := The effect of the declaration is the same
• If you need to declare it as a cyclic variable, the effect is different , var The declaration can survive until the end of the function , := The declaration method can only survive until the end of the cycle

Judgment and circulation

if, else if, else

package main

import (
	"fmt"
)

func main{
    
	if 1 >= 2 {
    
		fmt.Println("a")
	} else if 1 >= 3 {
    
		fmt.Println("b")
	} else {
    
		fmt.Println("c")
	}
}

• The judgment conditions are similar Python In the form of , There is no need for brackets , C Parentheses are mandatory in language
• If there are many conditions , You can use parentheses to prevent logical confusion

go There are only for loop

There are scope constraints that can be done

package main

import (
	"fmt"
)

func main{
    
	for i := 1; i < 10; i++ {
     
		//  The effect in uplink is equivalent to  C  In language  for (int i = 1; i < 10; i++)
		//  This is the circulatory body 
	}
}

If in for Don't write the cycle condition next , It will become an endless cycle , Here's the picture

package main

import (
	"fmt"
)

func main{
    
	//  It's a dead cycle 
	for {
    
		//  This is the circulatory body 
	}
}

Realization while loop

• Add the condition of jumping out of the loop in the loop body of the dead loop
• The sentence that jumps out still uses break

go Medium break and continue The function and usage of sentences are the same as those of other languages

switch sentence

And C The language is very similar

package main

import (
	"fmt"
)

func main{
    
	switch  expression {
    
		case : {
    
			
		}
		case : {
    
			
		}
	}
}

Function declaration

package main

import (
	"fmt"
)

func  Function name ( The name of the parameter 1  parameter types 1,  The name of the parameter 2,  parameter types 2)  Function return value type {
    
	//  The body of the function 
	return 
}

func main{
    
}

• If there are multiple formal parameters , Then follow the above format and so on
• go The language allows multiple function return values
• If there are multiple function return values, you need to write the return value type in parentheses

import

• Reference resources Python Medium import The form can be
• The library name needs to be caused by double quotation marks
• If only import A library may not use parentheses
• import The library contains multiple times , It needs to be enclosed in parentheses

Static type language

• go Language belongs to static type language
• After each variable is declared, the type cannot be changed , The content can be changed
• C, Java It's a dynamically typed language
• The characteristics of static types can help compilers perform compilation work faster , Increase of efficiency

Keep specific decimal output

• fmt.Printf() Use this
• Refer to C In language printf usage , Mostly the same , Formatting flags are partly different , Just consult the reference manual

big package

• Used to solve high-precision calculation
• The underlying principle is to perform large number operations based on strings , Refer to high-precision algorithm