About Go

@golanger Jongmin Kim The Go Programming Language

Overview
Introduction
Syntax
Features
URL shortener demo
Go trends

Go history
2007-09: Google's 20% project
2008-05: full-time project
2009-11: officially announced
Current: r59 stable release

Why a New Language?
Computers are enormously quicker but software development is not faster.
Dependency management is a big part of software development today.
Garbage collection and parallel computation are not well supported by popular systems languages.
Multi-core seen as crisis not opportunity.

To put it in a positive way
Go team's goal is to make programming fun again.
the feel of a dynamic language with the safety of a static type system
compile to machine language so it runs fast
real run-time that supports GC, concurrency
lightweight, flexible type system
has methods but not a conventional OO language
open source project, distributed under a BSD-style license.
Google App Engine gets support for Go.

package main import "fmt" func main() { fmt.Println("Hello, 안녕 ") } hello.go

Compiler
gc x86-64: 6g, 6l x86-32: 8g, 8l arm: 5g, 5l (incomplete)
gccgo - new frontend for gcc (gcc 4.6 or later)

Variables declaration
var i int
var s string
i = 15
s = "foo"
i := 15 s := "foo" i, s := 15, "foo" var ( i int s string )

Functions 1/3
func f() {
}
func f(i int) {
}
func f(i int) (bool) {
}
func f(i int) ( b bool ) { // named result parameter
b = true
return
}

Functions 2/3
// Multiple return values
func Open(path string) ( file *File, err Error ) {
}
file, err := Open("file")
file, _ := Open("file")

Functions 3/3
func main() {
f := func (s string) {
println("Hello, " + s)
}
callback(f)
}
func callback(f func(string) ) {
f("World")
}

if
if x > 0 {
return y
} else {
return x
}
if err := file.Chmod(0664) ; err != nil {
}

for
for {
}
for err != nil {
}
for i := 0; i < 10; i++ {
}
LOOP: for {
// do something
if error_occurred {
break LOOP
}
}
list := []string{"a", "b", "c"} for k, v := range list { }

switch
switch {
case a > b:
return true
case a < b:
return false
}
switch c {
case '+', '-', '*', '/' :
return true
}
return false
switch i { case 0: case 1: f() // f is not called when i == 0 } switch i { case 0: fallthrough case 1: f() // f is called when i == 0 }

Types
uint8
uint16
uint32
uint64
int8
int16
int32
int64
float32
float64
complex64 complex128 byte bool uint int uintptr string array slice map pointer // no pointer arithmetic const struct interface channel

Conversions 1/2
var f float32
var i uint32
f = 3.14159
i = uint32 (f)
fmt.Printf("%v, %v", i, f)
Output:
3, 3.14159

Conversions 2/2
mystring := "Hello, Go"
byteslice := []byte (mystring)
b := []byte{'H', 'e', 'l', 'l', 'o'}
s := string (b)

const
Constants can only be numbers, strings or booleans.
const ( FATAL = iota ERROR WARN INFO DEBUG TRACE ) const a = 1 const ( a = 1 b = "go" )

Arrays
var arr [3]int
arr[0] = 1
arr[1] = 2
arr[2] = 3
arr := [3]int{1, 2, 3} arr := [ ... ]int{1, 2, 3} ar := [2][3]int { [3]int{1, 2, 3}, [3]int{1, 2, 3} } ar := [2][3]int { [ ... ]int{1, 2, 3}, [ ... ]int{1, 2, 3} }

Slices 1/2
A slice is a reference to a section of an array.
ar := [3]int{1, 2, 3}
var sl []int // without a size
sl = ar[ 0:2 ]
fmt.Printf("%v", sl)
Output:
[1, 2]

Slices 2/2
ar[ :n ] == ar[0:n]
ar[ n: ] == ar[n:len(ar)]
ar[ : ] == ar[0:len(ar)]

Maps
var m map[string]int
monthdays := map [ string ] int {
" Jan ": 31 , "Feb": 28, "Mar": 31,
"Apr": 30, "May": 31, "Jun": 30,
"Jul": 31, "Aug": 31, "Sep": 30,
"Oct": 31, "Nov": 30, "Dec": 31 }
monthdays["Feb"] = 29
monthdays[" Unknown "] = 32

Structs
type Point struct {
x, y float64
}
var p Point
p.x = 7
p.y = 23.4
var pp *Point = new(Point)
*pp = p
pp.x = 3.14 // sugar for (*pp).x // There is no -> notation

new() vs make()
new returns pointers. t := new(T)
make returns initialized values. Use make to create slices , maps , and channels only. sl := make([]int, 10) // sl refers to a new array of 10 ints sl := new([]int, 10) // Allocates slice structure; *sl == nil

Methods
type Point struct {
x, y int
}
func (p *Point) Get () (int, int) {
return p.x, p.y
}
func (p Point) Put (x, y int) { // unexpected behavior
p.x = x; p.y = y
}

interfaces
type Point struct { x, y int }
func (p *Point) Get () (int, int) { return p.x, p.y }
func (p *Point) Put (x, y int) { p.x = x; p.y = y }
type Pointer interface {
Get() (int, int)
Put(x, y int)
}

delegation
type MorePointer struct {
Point // anonymous field
z int
}
func (p *MorePointer) Get() (int, int, int) {
return p.x, p.y , p.z
}
m := MorePointer{ Point{1, 2} , 3}
fmt.Println(m.Get())

defer 1/2
func ReadWrite() bool {
file.Open("file")
// do somthing...
if failureX {
file.Close()
return false
}
if failureY {
file.Close()
return false
}
file.Close()
return true
}
func ReadWrite() bool { file.Open("file") defer file.Close() // do somthing... if failureX { return false } if failureY { return false } return true }

defer 2/2
func f() {
for i := 0; i < 5; i++ {
defer print(i) // LIFO order
}
}
Output:
43210

goroutine 1/2
func ready(w string, sec int64) {
time.Sleep(sec * 1e9)
fmt.Println(w, "is ready!")
}
func main() {
go ready("Tee", 2)
go ready("Coffee", 1)
fmt.Println("I'm waiting")
time.Sleep(5 * 1e9)
}
Output:
I'm waiting <- Right away
Coffee is ready <- After 1 second
Tee is ready <- After 2 second

goroutine 2/2
goroutines were running concurrent, they were not running in parallel.
To run in parallel:
runtime.GOMAXPROCS(n)
or
GOMAXPROCS environment varaible

channel
c := make(chan int)
c <- 1 // send 1 on c (flowing into c)
<-c // receive value, throw it away
i := <-c // receive value, initialize i

channel
var c chan int
func ready(w string, sec int64) {
time.Sleep(sec * 1e9)
fmt.Println(w, "is ready!")
c <- 1
}
func main() {
c = make(chan int) // synchronous channels
go ready("Tee", 2)
go ready("Coffee", 1)
fmt.Println("I'm waiting")
ret := <-c
ret = <-c
}

You.rl with MongoDB (Simple URL shortener example)

Requirements
Create shortened URL. Do not duplicate keys
Save { "Shortened_URL" : "Long_URL" }
Redirect to long url when shortened URL requested

View source https://github.com/golang-korea/You.RL

You.rl demo

tools
gomake
goinstall
godoc
gofix
gofmt
gotest
cgo
......

Packages
http://golang.org/pkg/

Go project dashboard
http://godashboard.appspot.com/project

Try Go today! http://golang.org

http://twitter.com	15
http://www.saoona.com	14
http://prodtest.sophiaapp.com	7
http://us-w1.rockmelt.com	5
http://trunk.ly	4
https://twitter.com	3
http://contintavioleta.blogspot.com	1
http://shchoi82.tistory.com	1
http://blackboard.libertadores.edu.co	1

About Go

by Jongmin Kim on Sep 04, 2011

Accessibility

Categories

Tags

Upload Details

Usage Rights

9 Embeds 51

Statistics

About Go — Presentation Transcript