[Learn] GO language learning notes (i)

1. Variables

var < name > type

2. Initialization

var v1 int = 10

V3: = ten//v3 cannot be a variable that has already been declared

3. Ignore return values

_, _, Nick = GetName ()

4. Constants & Iota

Const Pi float64 = 3.1415

Const (

Size Int64 = 1024

EOF =-1

)

Const A, b, C = 3, 5, "XX"

Const (

V1 = 1 << Iota

V2

V3

)//Iota increment starting from 0 before the next const

　　　　

5. Os. GETENV ("HOME")

6. Start with uppercase, visible outside the package

7. UIntPtr

Floating point comparison--using poor precision

8. plural

v = Complex (3.1, 3.2)

Real (v) = = 3.1

Imag (v) = = 3.2

9. String, cannot be assigned as [x]

10. String type

BYTE---uint8

Rune----Unicode Characters

11. Array declarations

var array_ex [32]byte = [32]byte {1, 2, ...}

Len ()

For the value type, in the fun internal modification, does not affect the fun external value

12. Array slicing

var MyS []int = Array_ex[:5]

var MYSL = make ([]int, 5)

Mysli: = []int{1, 2, 3}

Len/cap/append.

Len (slice) = number of elements

Cap (slice) = memory already allocated

. Append ()

MyS = Append (MyS, 1, 2, 3)

MyS2: = []int{8, 9, 10}

myS3 = Append (MyS, myS2 ...) Break myS2, join with multiple elements, append parameter requirements

14.copy ()

Copy (s1, S2)//Smaller to determine the size of the copy

15.

Map

var persondb map[string] PersonInfo

Persondb = Make (map[string] PersonInfo)

persondb["123"] = personinfo{"123", "Tom", "203"}

　　

person, OK: = persondb["123"]

If OK XXX

MyMap = Make (map[string] PersonInfo, 100)

Delete (MyMap, "123")

16.

If return else return

Need a final return

Fallthrough.

Switch X {

Case 0:

....

Fallthrough//Continuation case

Default

}

. for {infinite loop

No while statement

. Goto

20. Functions

Func <func-name> (var ...) (ret ...) { ...

21. Indeterminate Parameters

Func myFunc (args ... int) {

For _, arg: = Range args {

}

}

Call

Myfun ([] int {1, 2, 3, 5})

Parameter passing:

Fun A (args ... int) {

B (args ...)

C (args[1:] ...)

}

22. Any type

Func Printf (format string, args ... interface{}) {

Func myprint (Args ... interface {}) {

For _, arg: = Range args {

Switch arg. (type) {

Case INT:

Case string:

Default

}

}

}

23. Multiple Return values

Carry Error

_: Ignore return value

24. Anonymous functions

F: = Func (A, b int, z float64) bool {

}

Func (ch Chan int) {

CH <-ACK

} (Reply_chan)

25. Closures

Func Main () {

var J int = 5

A: = Func () (func ()) {//parameter is NULL, return value is a function

var i int = 10

Return Fun () {

} ()

}

A ()

J *= 2

A ()

errno.

Defer fun () {//do complex cleanup work

It will be called no matter what.

Panic () Recover ()

Panic () immediately terminates, returns the call, defer is called

Recover () Handling panic exceptions

Defer func () {

If r: = Recover (); R! = Nil {

Log. Printf ("Return:%v", R)

} ( )

}

Flag Package: Command-line argument parsing

X = flag. String ("..... ")

Flag. Parse ()//called in Main, parameter resolved to value in X

　　

File, err: = OS. Open ()

Defer file. Close ()

values = Make ([]int, 0)

for {

Line, Isprefix, err1: = Br. ReadLine ()

Err1! = Nil; Err1! = Io. Eof

}

str: = string (line)

Value, err1: = StrConv. Atoi (str)

If err1! = nil ...

Values = Append (values, value)

writevalues func (values [] int, outfile string)

File, err: = OS. Create (outfile)

str: = StrConv. Itoa (value)

File, err: = OS. Open (infile)

Defer file. Close ()

BR: = Bufio. Newreader (file)

Line, Isprefix, err1: = Br. ReadLine ()

Err1! = Nil, err1! = Io. Eof

T1: = time. Now ()

[Learn] GO language learning notes (i)