Go basic constant definition and use

Definition and use of basic constants ：

Constants define code instances

package main

func main() {
	//  Constant definition ： Can be called , It cannot be modified 
	const PI = 3.1415926
	r := 2.0
	println(2*PI*r)

	//  Set law defines constants 
	const (
		MALE = 1
		FEMALE = 2
	)
	println(MALE, FEMALE)

	//  Constant group definition considerations ,  If the type and initial value are not specified , Keep consistent with its previous line 
	const (
		x int = 16
		y
		s string = "goho"
		z
	)
	println(x, y, s, z)

	// Constant considerations ：
	// 1. The data type of a constant can be Boolean 、 Numbers and strings 
	// 2. Constants that have not been used will not report errors when compiling 
	// 3. Constant group definition considerations ,  If the type and initial value are not specified , Keep consistent with its previous line 

}

Running results ：

iota Constant counter ：

itoa yes go Language Constant automatic generator in , It doesn't follow c Language like enumerations can be generated implicitly , You must explicitly specify , The specific syntax is as follows ：

1. Constant combination assignment ,iota The default from the 0 Start , Add one more each time ：
2. Every time iota Meet a new one const, It will reset to 0：
3. Assign values to the same line ( List assignment ),itoa The value of does not change ：

go Definition

package main

func main() {
	// const Of iota Constant counter ,
	//  Constant definitions without expressions reuse the previous line of expressions 
	const(
		a = iota	// The default from the 0 Start 
		b
		c
	)
	println("iota Constant ：", a, b, c)

	 // each const Of iota Constant modules do not interfere with each other 
	const (
		x = iota
		y
		z
	)
	println(" each iota Constant modules do not interfere with each other ：", x, y, z)

	//  How to learn from other non 0 How about the number 
	//  Constant definitions without expressions reuse the previous line of expressions 
	//  Pay attention to the meaning of adding one line by line 
	const (
		aa, bb = iota, iota
		cc = 10
		dd, ee = iota, iota
	)
	println(aa, bb, cc, dd, ee)
}

Running results ：