GO language Learning

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

Installation:

sudo apt-get installgolang-go

Export goroot= $HOME/go

Exportpath= $PATH: $GOROOT/bin

One,Hello World program

Package main//This packet is named import "FMT"//contains "FMT", in FMT there is input output func main () {FMT. Printf ("Hello world!\n");}

Note : the main () function, curly brace "{", is the same line as the function name , and the compiler will give an error if the C language is the same.

Compile:

Go Build A.go

the a.go here is the source file name

Two use hash table

Package main import ("FMT") type Data struct{date string; value int;} func main () {FMT. Printf ("Hello world!\n"); var m = make (Map[string]int); Create a blank hashm["str1"] = 10; m["str2"] = 1000; Fmt. Printf ("%d\n", m["str1"]); Traverse hashfor name,value: = range m {fmt. Printf ("%s\t%d\n", Name,value); } }

Three-assignment statement features

googledocument References:

Multipleassignment

Thelanguage specification has long guaranteed, in assignments theright-hand-side expressions is all evaluated before Anyleft-hand-side expressions is assigned. To guarantee Predictablebehavior, Go 1 refines the specification further.

Ifthe left-hand side of the assignment statement contains expressionsthat require evaluation, such as function calls or AR Ray Indexingoperations, these'll all is done using the usual left-to-right rulebefore any variables is assigned their V Alue. Once everything isevaluated, the actual assignments proceed in Left-to-right order.

Theseexamples illustrate the behavior.

SA: = []int{1, 2, 3}    I: = 0     i, sa[i] = 1, 2  //sets I = 1, sa[0] = 2     SB: = []int{1, 2, 3}    J: = 0     Sb[j], j = 2, 1  //sets Sb[0] = 2, j = 1     SC: = []int{1, 2, 3}     sc[0], sc[0] = 1, 2  //sets Sc[0] = 1, then sc[0] = 2 (so sc[0] = 2 at end)     

Updating : This is a change where tools cannot help, but breakage is unlikely. No code in the repository is broken by this change, andcode that depended on the previous unspecified behavior W As Alreadyincorrect.

Definition and use of four functions

Package main import ("FMT")//  (x int) is the parameter table//(r int) is the return result of the Func fun (x int) (r int) {if x = = 1 {return 1;} else {return Fun (x-1) * x;} return; } func Main () {FMT. Printf ("%d\n", Fun (3)); }

Wuchang Quantity and variable

Package main import ("FMT" "OS") const PI = 3.14; Defines a constant variable, a const PP = 2/3; Func main () {var a int = 10;//defines an integer variable and is initialized to 10var goos = os. Getenv ("PATH"); Gets the system environment variable FMT. Printf ("%s\n", GOOS); Fmt. Printf ("%f\n%d\n", pi,pp); Fmt. Printf ("%d\n", a); }

Six Time savers:short Declarations anddistributing

Before defining a variable method:

var a int = 10;

To save time, we can define the following:

A: = 10;

The system defines a variable based on the type of the number

Seven basic data types

Number:

int, uint, float, uintptr

The UIntPtr data type is a special data typethat are an

Unsigned integer that would be large Enoughto store a pointer

Value.

int, uint, floatthe length is based on the platform, if it is64bitplatform,Intand theUIntlength is64bit, if it is+ bitPlatform,the length of it is32bit;

The architecture-independent numeric typesare:

Uint8

Uintl6

UInt32

UInt64

int8

Intl6

Int32

Int64

Float32

Float64

Byte(Thebyte is a familiar alias for Uint8. )

Note:

{

var a int8 = 10;

var b int16 = 100;

b = A;

}

This program would generate a compiler error:

Cannot use Rny16bitint (type Int16) as

Type Int32 in Assignment

String:

var str string;// definition

str = "Abcdeft";

Fmt. Printf (str);// output

Str[0] is 'a ',index starting from 0

Eight use Strings Package

Strings. Hasprefix (strstring, prefix string) bool;//determine if there is a prefix prefixstrings. Hassuffix (strstring, suffix string) bool;//determine if there is a suffix suffixstrings. Count (strstring,sub string) int;//calculate how many substring substrings. Index (str string, sub string) int;strings. Lastindex (str string, sub string) int; return-1strings if not found. Repeat (str string, Count int) string;//copies str several times, returning the copied string for example: str = "abc"; str1 = strings. Repeat (str,3);//At this point the value of STR1 is abcabcabcstrings. ToUpper (str string) string;strings. ToLower (str string) string;

Nine Strconvpackage Use

Package Mainimport ("FMT" "StrConv") func main () {var II int = 1100;var str2 String;var str1 = "1235"; var err error;ii,err = StrConv. Atoi (STR1); if err = = Nil {fmt. Printf ("%d\n", ii);} STR2 = StrConv. Itoa (ii); FMT. Printf (STR2);}

Ten conditional statements

If condition {} else {}//********************************if initialization_ Statement Condition {} else {}//*****switch**********************************************package mainimport ("FMT") Func Main () {var a int = 100;switch a {case  100:fmt. Printf ("a<100\n"); case  111:fmt. Printf ("a > 111\n");d efault:}}//----------------------------------------------------------------------------- --------------Package Mainimport ("FMT") func main () {var-a int = 100;switch {case  a< 100:fmt. Printf ("a<100\n"); case  a > 111:fmt. Printf ("a > 111\n");d efault:fmt. Printf ("else\n");}} //***************************************************

11 Loop Iteration

/******************************************************************package mainimport ("FMT") func main () {for i:= 0; I < 100; i++ {fmt. Printf ("%d", I);}} //----------------------------------------------------------------------------------------------------------

12 Custom Functions

1. Func fun (a int) int {

}

2. Func Fun (A, b int) (int, int) {

return a, B;

}

in the go language, it is allowed to return multiple values

13 using defer(delay)

Package Mainimport ("FMT") func fun1 () {fmt. Printf ("abc\n");d efer fun2 ();//wait until the end of fun1 execution, and then automatically execute fun2 (); fmt. Printf ("eft\n");} Func fun2 () {fmt. Printf ("fun2\n");} Func Main () {fun1 ();}

14 using blank identifier "_"

Package Mainimport ("FMT") func fun1 () (int, int) {return 1, 2;} Func main () {var a int;a,_ = Fun1 ();//Use  _ to record the return value not recorded in FMT. Printf ("%d\n", a);}