Shulou(Shulou.com)06/03 Report--

Features:

a. Automatic garbage collection

b. Rich built-in types

c. Multiple return values of function

d. Error handling

e. Anonymous functions and closures

f. Type and interface

G.goroutine concurrent programming

h. Reflection

I.CGO calls c function

The go language starts with the main function in the main package, and the Go language main () function cannot take parameters or define a return value. The parameters passed in on the command line are saved in the os.Args variable. If you need to support command line switches, you can use the flag package. After the package declaration, a series of import statements are used to import the package that the program depends on.

Package main

Import "fmt" / / We need to use the Println () function in the fmt package

Func main () {

Fmt.Println ("Hello, world. Hello, World!")

}

"go run hello.go

"go build hello.go

1. Variable

= assignment operator

: = type inference with initial value attached

a. Declaration of various variables

Var v1 int

Var v2 string

Var v3 [10] int / / array

Var v4 [] int / / Array slice

Var v5 struct {

F int

}

Var V6 * int / / pointer

Var v7 map [string] int / / map,key is string type, value is int type

Var v8 func (an int) int

Const zero = 0.0

b. Class when a variable is declared

Var v1 int = 10 / / correct usage 1

Var v2 = 10 / / correct usage 2, the compiler can automatically deduce the type of v2

V3: = 10 / / the correct use mode 3, the compiler can automatically deduce the type of v3

Go is a strongly typed language. You can specify the data type when defining a variable, or you can choose to derive it automatically.

c. Variable assignment

I, j = j, I / / supports multiple assignments

d. The anonymous variable "" represents

Suppose the GetName () function is defined as follows, and it returns three values, namely firstName, lastName, and

NickName:

Func GetName () (firstName, lastName, nickName string) {

Return "May", "Chan", "Chibi Maruko"

}

If you only want to get the nickName, the function call statement can be written as follows:

NickName: = GetName () assume that the definition of the GetName () function is as follows, which returns three values, firstName, lastName, and

NickName:

Func GetName () (firstName, lastName, nickName string) {

Return "May", "Chan", "Chibi Maruko"

}

If you only want to get the nickName, the function call statement can be written as follows:

, _, nickName: = GetName ()

e. Constant, adding const when defining

Const Pi float64 = 3.14159265358979323846

Const zero = 0.0 / / untyped floating point constant

Const (

Size int64 = 1024

Eof =-1 / / untyped integer constant

)

Const u, v float32 = 0,3 / / u = 0.0,v = 3.0,multiple assignment of constant

Const a, b, c = 3,4, "foo"

/ a = 3, b = 4, c = "foo", untyped integers and string constants

f. Enumerate

The following is a general enumeration representation that defines a series of integer constants:

Const (

Sunday = iota

Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

NumberOfDays / / this constant is not exported

)

Like other symbols in the Go language (symbol), constants that begin with uppercase letters are visible outside the package.

In the above example, numberOfDays is private within the package, and other symbols can be accessed by other packages.

Data types of g.go language

 Boolean type: bool.

 integers: int8, uint8, byte, int16, int, uint, int32, int64, uintptr, etc.

 floating point type: float32, float64.

 plural type: complex64 (plural type consisting of 2 float32), complex128. 2i 3i

 string: string.

 character type: rune. Represents a single Unicode character.

 error type: error.

In addition, the Go language supports the following composite types:

 pointer (pointer)

 array (array)

 slice (slice)

 Dictionary (map)

 Channel (chan)

 structure (struct)

 Interface (interface)

String value and its traversal

Str: = "Hello, World"

N: = len (str)

For I: = 0; I < n; iTunes + {

Ch: = str [I] / / str [I] = "x"; error, the string cannot be changed again, the array is fine

Fmt.Println (I, ch)

}

The use of arrays

[32] an array of 32 byte / / length, with one byte for each element

[2N] struct {x, y int32} / / complex type array

[1000] float64 / / pointer array

[3] [5] int / / 2D array

[2] [2] [2] float64 / / is equivalent to 2

Var myArray [10] int = [10] int {1,2,3,4,5,6,7,8,9,10}

MySlice: = myArray [:] / / create array slices based on all elements of myArray

MySlice: = myArray [: 5] / / create array slices based on the first five elements of myArray

MySlice: = myArray [5:] / / create an array slice based on all elements starting with the fifth element

MySlice: = make ([] int, 5) / / create an array slice with an initial number of 5 elements with an initial value of 0:

MySlice: = make ([] int, 5,10) / / create an array slice with an initial number of elements of 5, with an initial value of 0, and reserve storage space for 10 elements: len (mySlice) = 5

Cap (mySlice) = 10, mySlice = append (mySlice, 1,2,3), any array can grow dynamically

MySlice: = [] int {1, 2, 3, 4, 5} / / directly create and initialize array slices containing 5 elements:

For _, v: = range myArray {/ / array traversal

Fmt.Print (v, "")

}

For I: = 0; I

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