Go learning notes (5) basic types and declarations (4)

Today is the Lantern Festival , Have you eaten glutinous rice balls ？

Go on go Basic type .

Constant

Like any other language ,go Constants can also be defined .

const x int64 = 100

Basically and var It's similar to .

stay go In language ,const It is equivalent to naming literal quantity , It can only save values that the compiler can get at compile time . There are about the following categories ：

• Numerical literals
• true and false
• character string
• character
• Built in functions complex、real、imag、len And cap
• An expression that can determine the value at compile time

go There is no guarantee that a value calculated at run time will remain unchanged .

Typed and untyped constants

Constants can be typed or untyped .

Typeless constants are just like literal quantities , It has no type itself , But if you can't infer the type when using , Then it will be the default type of its literal .

const a = 123

var b int = a
var c float64 = a
d := a

Typed constants can only be evaluated and assigned to variables of the same type .

Unused variables

go There is a very strong grammatical rule ,go Require every defined local variable Must be used . Otherwise, a compilation error will be reported . This can greatly reduce code redundancy , Improve code quality .

however go Compiler checking is relatively loose , As long as the variable is read once, no error will be reported , Even if you assign a value to a variable but don't use it later .

func main(){
    
	x:=123
	fmt.Println(x)
	x=10
}

If you want to find such problems, you can use golangci-lint

go Languages can define unused Package level variables .

go Language allows creation of Unused constants .

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