GO language variables and data types

1. variable

1.1 variables are defined using the keyword var. Variables are strongly typed.

Package main

Import "fmt"

Var I int
Var c, python, java bool

Func main (){
Fmt. Println (I, c, python, java)
}

1.2 When defining a variable, you can get the type by assigning values instead of specifying the type.

Package main

Import "fmt"

Var I, j int = 1, 2
Var c, python, java = true, false, "no! "

Func main (){
Fmt. Println (I, j, c, python, java)
}

1.3 define temporary variables in the function by: =

Package main

Import "fmt"

Func main (){
Var I, j int = 1, 2
K: = 3
C, python, java: = true, false, "no! "
Fmt. Println (I, j, k, c, python, java)
}

2. data type

2.1 all data types

Bool

String

Int int8 int16 int32 int64
Uint uint8 uint16 uint32 uint64 uintptr

Byte // alias for uint8

Rune // alias for int32
// Represents a Unicode code point

Float32 float64

Complex64 complex128

2.2 all data types must be converted. Otherwise, compilation errors may occur.

Var I int = 42
Var f float64 = float64 (I)
Var u uint = uint (f)

2.3 constants

A constant can be a number, string, character, or Boolean type.
The declaration of a constant is the same as that of a variable, but the const keyword is added before it.
Constants cannot be used: = value assignment

Package main

Import "fmt"

Const Pi = 3.14

Func main (){
Const World = "World"
Fmt. Println ("Hello", World)
Fmt. Println ("Happy", Pi, "Day ")
Const Truth = true
Fmt. Println ("Go rules? ", Truth)
}

3. struct

Struct is almost the same as the C language and is defined using the tpye and struct keywords.

Package main

Import "fmt"

Type Vertex struct {
X int
Y int
}

Func main (){
Fmt. Println (Vertex {1, 2 })
}

3.1 Use "point" to access the variables in the structure

Package main

Import "fmt"

Type Vertex struct {
X int
Y int
}

Func main (){
V: = Vertex {1, 2}
V. X = 4
Fmt. Println (v. X)
}

It is not perfect to have no struct in Java. Defining a struct requires writing a lot of code.

3.2 assign values to variable names during construction

Package main

Import "fmt"

Type Vertex struct {
X, Y int
}

Var (
P = Vertex {1, 2} // has type Vertex
Q = & Vertex {1, 2} // has type * Vertex
R = Vertex {X: 1} // Y: 0 is implicit
S = Vertex {} // X: 0 and Y: 0
)

Func main (){
Fmt. Println (p, q, r, s)
}