WebSummit 2015 - Gopher it

https://ﬂic.kr/p/7bgkPn
Gautam Rege

https://ﬂic.kr/p/7bgkPn
https://ﬂic.kr/p/9HfsBe
Gautam Rege

Rethink Programming
Why Go?
• See various features of Go
• Go code snippets
• Lot’s of gopher cartoons

@joshsoftware
Where Programming an Art!

Why was another
language required?
Arn’t there enough already?
https://ﬂic.kr/p/bk3mFf

Picking a language?
Safety Speed
Ease
?
Type
Syntax Compilation
Runtime
IPC

Picking a language?
Safety Speed
Ease
?
Type
Syntax
Readable
Maintainable
Learning
Compilation
Runtime
IPC

Inspiration for Go
https://speakerdeck.com/bg/the-roots-of-go

Go is C on Steroids
No more
memory leaks

Go is C on Steroids
No more
memory leaks
Maps, Slices
Closures
Concurrency

Go is C on Steroids
No more
memory leaks
Maps, Slices
Closures
Concurrency
go fmt
go build
go get
go ﬁx

Concurrency
Parallelism
Multi-core Processing
Concurrency is not Parallelism

Concurrency
Independent executing components
Parallelism
Execution in parallel

“Don’t communicate
by sharing memory.
Share memory by
communicating.”
Rob Pike

Concurrency and Parallelism
1 2 3 4

CSP
Communicating Sequential Processes
https://ﬂic.kr/p/6MwYFo

CSP
Communicating Sequential Processes
https://ﬂic.kr/p/awu6ZA
since 1978 !!
https://ﬂic.kr/p/6MwYFo

type Attendee struct {
Name string
Country string
phone string
ticket string
}
type Speaker struct {
Attendee
slot time.Time
}
type Conference struct {
Name string
Location string
people []*Attendee
}
Access
Speciﬁers

Export with Case Sensitiveness
Exported / Unexported
“Nothing is really protected”
Name string
Country string
phone string
ticket string
}
Attendee
slot time.Time
}
Name string
Location string
people []*Attendee
}
Access
Speciﬁers

Structs, not classes
Embedded structs
Name string
Country string
phone string
ticket string
}
Attendee
slot time.Time
}
Name string
Location string
people []*Attendee
}
Inheritance

Embedded structs
Name string
Country string
phone string
ticket string
}
Attendee
slot time.Time
}
Name string
Location string
people []*Attendee
}
Inheritance
m
m

Embedded structs
Name string
Country string
phone string
ticket string
}
Attendee
slot time.Time
}
Name string
Location string
people []*Attendee
}
Inheritance
m
m
m

func (c *Conference) BuyTicket() (ticket string, err error)
{
//payment gateway stuff
return "R-00001", nil
}
func (person *Attendee) Attend(c *Conference) bool {
ticket, err := c.BuyTicket()
if err != nil {
// handle error
}
person.ticket = ticket
return true
}
Functions with Receivers

type SocialNetworker interface {
OnFacebook() string
OnTwitter() string
}
Interfaces
Don’t implement interfaces.
They happen!

type SocialNetworker interface {
OnFacebook() string
OnTwitter() string
}
Interfaces
func (Attendee) OnFacebook() string {
return “my fb account"
}
func (Attendee) OnTwitter() string {
return "my twitter account"
}
func (Conference) OnFacebook() string {
return "conf fb account"
}
func (Conference) OnTwitter() string {
return "conf twitter account"
}

Polymorphism
var social SocialNetworker
social = me // Attendee
fmt.Println("me: ", social.OnFacebook())
social = c // Conference
fmt.Println("me: ", social.OnFacebook())

y := 2 // y is of type int
y = "3"
Programming Awareness

y := 2 // y is of type int
y = "3"
Compile Error
Did you just
assign a string
to an integer?

confs := make(map[string]Conference)
for key, value := range confs {
fmt.Println(value.Name)
}

confs := make(map[string]Conference)
for key, value := range confs {
fmt.Println(value.Name)
}
Just saying - you should not
iterate a hash, man!
I’l randomise the order now!

defer
func trace(s string) { fmt.Println("entering:", s) }
func untrace(s string) { fmt.Println("leaving:", s) }
func main() {
trace("main")
defer untrace("main")
// do your thing.
}

defer
func trace(s string) { fmt.Println("entering:", s) }
func untrace(s string) { fmt.Println("leaving:", s) }
func main() {
trace("main")
defer untrace("main")
// do your thing.
}
func trace(s string) string {
fmt.Println("entering:", s)
return s
}
func main() {
defer untrace(trace(“main”))
// do your thing.
}

1 2 3 4
Goroutines

1 2 3 4
Channels

Ah… Some Go code (ﬁnally)
package main
import (
"fmt"
"runtime"
"sync"
)
var wg sync.WaitGroup
/*
* Each go-routine sleeps at random(1-5) seconds.
* This is simulating long working process
* Then we finish in order
*/
func check_baton(leg int, baton chan int) {
for value := range baton {
switch value {
case leg:
// pass the baton
fmt.Println("Finished leg ", leg)
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
func run(leg int, baton chan int) {
defer wg.Done()
fmt.Printf("Leg %d.. churningn", leg)
// Massive CPU churn
for count := 0; count < 300; count++ {
for char := 0; char < 30000; char++ {
fmt.Printf("")
}
}
fmt.Printf("Leg %d.. churned, waiting to exitn", leg)
check_baton(leg, baton)
}
func main() {
runtime.GOMAXPROCS(4)
baton := make(chan int)
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
// wait for relay to finish
wg.Wait()
}

Packages
package main
import (
"fmt"
"runtime"
"sync"
)
/*
*/
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
defer wg.Done()
fmt.Printf("")
}
}
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}
package main
import (
"fmt"
"runtime"
"sync"
)

Channels
package main
import (
"fmt"
"runtime"
"sync"
)
/*
*/
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
defer wg.Done()
fmt.Printf("")
}
}
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}

Go Routines
package main
import (
"fmt"
"runtime"
"sync"
)
/*
*/
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
defer wg.Done()
fmt.Printf("")
}
}
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}

Writing to a Channel
package main
import (
"fmt"
"runtime"
"sync"
)
/*
*/
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
defer wg.Done()
fmt.Printf("")
}
}
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}

Goroutines and defer
package main
import (
"fmt"
"runtime"
"sync"
)
/*
*/
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
defer wg.Done()
fmt.Printf("")
}
}
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}
defer wg.Done()
fmt.Printf("")
}
}
fmt.Printf("Leg %d.. churned, waiting to exit
n", leg)
}

Reading from a Channel
package main
import (
"fmt"
"runtime"
"sync"
)
/*
*/
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}
defer wg.Done()
fmt.Printf("")
}
}
}
func main() {
wg.Add(4)
for i := 1; i < 5; i++ {
go run(i, baton)
}
// start the race
baton <- 1
wg.Wait()
}
switch value {
case leg:
// pass the baton
if leg == 4 {
close(baton)
} else {
baton <- leg + 1
}
return
default:
// ignore
baton <- value
}
}
}

Smart City Technology
• Help / Panic / 911
• Complaints
• e-Wallet & e-Shopping
• Hospital Admission
• e-Cycle Management
• Township Surveillance
• Visitor Management
Utility Metering & Billing
• Water
• Electricity
• Gas
• Smart Distribution Box
Communication
• Internet
• DTH
• Telephony
• Video On Demand
• e-Learning
• Parking Management
• Bank Auto-debit
• Township Smart Debit card
• Hospital Admission
• e-Cycle Management
• Digital Door Locks
• Asset Tag Tracking
• Smart Street Lighting
Services
Security

Building Smart Circuits
modbus
Ethernetmbus
wmbus
zigbee

Golang References
http://golang.org
https://tour.golang.org
https://golang.org/doc/effective_go.html
https://groups.google.com/group/golang-nuts
https://golang.org/play
http://blog.gopheracademy.com
http://www.goinggo.net
http://golang-challenge.com

Let the games begin !
@gautamrege
Gophers
@joshsoftware

WebSummit 2015 - Gopher it

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WebSummit 2015 - Gopher it