2. Golang Basics-variables, types, keywords ...

This is a creation in Article, where the information may have evolved or changed.

First Program

package mainimport "fmt"var s = "hello"  //全局变量func main() {fmt.Println(s, "world")}

go run hello.goOutput

hello world

2.1 Variables

Go uses the keyword var to define the variable, and the type information is placed behind the variable name and initialized to zero, as follows:

var s string  var x intvar (   //批量声明a intf float64x string)

There's a more concise way to define inside a function. ：=

func main() { s := "string" //局部变量}

Variable assignment, two variables can be exchanged directly

var i, j inti, j = j, i

Note: The compiler will error if the variable defined inside the function is not used.

declared and not used

2.2 Constants

With the keyword const definition, the constant value must be a numeric value that can be determined during compilation.

const Pi  

Enumeration iota , which starts from 0 by the number of rows, and if it const is re-calculated again starting from 0.

const (Sunday = iota  // 0Monday         // 1Tuesday        // 2Wednesday      // 3Thursday       // 4Friday         // 5Saturday       // 6)

2.3 Types

Go includes the following basic types:

• Boolean type: BOOL.
• Integral type: int8, Byte, int16, int, uint, uintptr, etc.
• Floating point types: float32, float64.
• Plural type: complex64, complex128.
• Character: String.
• Character type: Rune.
• Fault type: Error.

There are also complex types: slice, map, and so on.

2.4 Key Words