Go environment and variable data types

Environment

Go Download Install

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A fool-type installation can

Open cmd after installation, enter go version the successful output version number to indicate successful installation

Go Environment variables

A question about the environment variables of Go Seaconch just suddenly thought of the more appropriate way to describe

1. Goroot

Goroot is often described as the path to the Go compiler

Goroot do not need us to match , generally the path chosen when installing the GO compiler is the goroot path

Seaconch added: When you import a package, the native pkg is also referenced by Goroot.

So the students who have used NPM can understand that: Global package path

2. Gopath

Gopath is often described as the Go Source (engineering) path

Gopath need us to manually configure , of course, if just write a demo practiced hand, not worthy of it

Seaconch thinks Gopath is a bit like NPM's local package path

3. Supplement

This is not to say that you cannot introduce packages under either of these two directories, for example we can pass the . /pkg 's way of introducing and using our own packages is no problem, and as long as the relative path relationship remains the same, the copy can be run anywhere, and the downside is not to execute the go install command

Hello World Scout

Create a new Notepad in any location

Enter the following code

package mainimport "fmt"func main () {    fmt.Println("seaconch.")}

Save the file as a.go Note the suffix name to ensure that it is not a. txt

Run the cmd input on the path where the A.go is locatedgo run a.go

You can see that the seaconch has been successfully exported.

输出中文的小伙伴现在还不要着急，因为目前还不是 utf-8 编码

Common commands

Go Run xxx.go

Debug artifacts without a build to execute code directly; In special cases, batch run is required, for example go run main1.go main2.go

注： main1.go 与 main2.go 同包 并属于 extension 关系

Go Build Xxx.go

Compile the source code, generate executable programs, and in special cases require batch compilation, for examplego build main1.go main2.go

Go Install

Compile the build project executable file, which is generated by default in the bin directory in the gopath directory

Variables and data types

Variable

Define VARIABLE:VAR variable name type

Give me a chestnut.

• var _name string
• VAR (
• _name string
• _age int
• )

Simple define: Variable name: = Expression

This method applies only to the inside of the function

Give me a chestnut:

• _name: = "Seaconch"
• _name, _age: = "Seaconch", 99

注：变量名称区分大小写

Characteristics

In the Go language, there are three distinct features in the operation of a variable.

1. :=This method only applies to variables that have not been define , and can only be used inside the func
2. x, y := y, xThe classic variable exchange is a very simple issue in the Go language, just like this.
3. _Because the go language, multiple return values are particularly common, when we only need multiple return values of the individual values, you can use the name, _: = Method () to discard the second return value, a similar way to achieve the desired effect

Constant

Constants need to have an initial value

Define

Give me a chestnut:

Const _PI float64 = 3.14 / const _version String = "v1.0"

Multi-assigned value

Const (

A = 1BC = 2D

)

In multi-assignment cases, constants that are not assigned by default use the value of the previous constant, so B = 1, D = 2

To represent an enumeration by using Iota :

const (    sunday = iota    monday    tuesday    wednesday= 88    thursday     friday = iota    saturday)

Sunday-0

Monday-1

Tuesday-2

Wednesday-88

Thursday-88

Friday-5

Saturday-6

Can see the role of Iota, Iota is a bit like a counter , seaconch, use this small example to illustrate its use

Integer

int shaping, based on CPU & IDE Decision 64/32

UINT unsigned int

byte = = Uint8 can be understood as type aliases

Rune = = Int32 can be understood as type aliases

Floating point

Float32/float64 accuracy is different

Plural skip

Boolean type

The Boolean type has two points that need to be mainly:

1. The default value is False
2. Golang 1 with true 0 is not comparable to false

String

To intercept a string:

_str := "hello seaconch."    fmt.Println(_str[:]) -> hello seaconch.    fmt.Println(_str[7:]) -> eaconch.    fmt.Println(_str[:8]) -> hello se        fmt.Println(_str[7:8]) -> e

Look at the code knowing ~

7 Index of <= target string < 8

All right, let's get here today.