Introduction to Go programming language

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Quick overview of Google Go programming language

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Introduction to Go programming language

  1. 1. Introduction toGoSlawomir Dorzak@sdorzak
  2. 2. About this presentation● The point is to give you a "taste" of Go, notto teach you how to programming in it● I assume you know what an array and apointer is● Im not a Go expert
  3. 3. Quick history● Invented by Robert Griesemer, Rob Pikeand Ken Thompson in 2007 (public in 09)● Born out of a need for ease of programmingcombined with type safety and portability● Other goals:○ Easy to learn○ Type safety and memory safety○ Easy concurrency via channels and "goroutines"○ Low latency garbage collection○ Fast compilation
  4. 4. Who is Ken Thompson?
  5. 5. Some companies using Go● Canonical● BBC● Heroku● CloudFoundry● CloudFlare● Bit.ly● Google
  6. 6. IDE options● Sublime Text 2● IntelliJ● LiteIDE● Intype (Windows only)● Netbeans● Eclipse● TextMate● Komodo● Zeus (Windows only)
  7. 7. Syntax overview● It looks similar to C● End of line semicolons are optional● Variable declarations are optional○ variable name is followed by its type■ var s string○ variables can also be declared by initialization■ i := 0● Type conversions must be explicit● Visibility is controlled using capitalization eg.○ func Foo() will be publicly visible outside thedefining package○ func bar() will be private
  8. 8. Interesting caveats● Unused variables are a compilation error● Unused import directives also● No classes - Go is a procedural language● No overloading● No inheritance
  9. 9. Control structures● If● For● SwitchThats it!
  10. 10. Control structures samplesif v := math.Pow(x, n); v < lim {return v} else {fmt.Printf("%g >= %gn", v, lim)}
  11. 11. Control structures samplesfor i := 0; i < 10; i++ {sum += i}for sum < 1000 {sum += sum}for {}
  12. 12. Control structures samplest := time.Now()switch {case t.Hour() < 12:fmt.Println("Good morning!")case t.Hour() < 17:fmt.Println("Good afternoon.")default:fmt.Println("Good evening.")}
  13. 13. Types● Boolean - bool● Numeric - uint8 to uint64, int8 to int64, uint, int, float32, float64,complex64, complex128, byte, rune● String - string● Array eg. [5]byte, Slice eg. make([]int, 50, 100), Map eg. map[string]int● Struct - struct● Pointer - *● Function - func● Interface - interface● Channel - chan
  14. 14. Array● Numbered sequence of elements of a singletype● Fixed size● Always one dimensional but can becombined● eg.○ [32]byte○ [2][8]int○ [5]myStruct○ [3]SomePublicInterface○ [2]struct { x, y int32 }○ b := [...]string{"Penn", "Teller"}
  15. 15. Slice● Represents a segment of an array● Like array - slice is one dimensional● Slice does not have a fixed length● Once initialized is always associated withand underlying array● Creating a slice:○ make([]int, 50, 100)○ new([100]int)[0:50]○ letters := []string{"a", "b", "c", "d"}
  16. 16. Map● Its a hash table implementeation in Go● Provides fast lookup by given key● Key can be any type that is comparable● Value can be any type including anothermap● Order is not guaranteed● Maps are not safe for concurrent use!m := make(map[string]int)m["val1"] = 1m["val2"] = 2for key, value := range m {fmt.Println("Key:", key, "Value:", value)}
  17. 17. Struct● Structs are declared using struct keyword● Only fields can be defined inside a structtype Vertex struct {X intY int}p := Vertex{1, 2}
  18. 18. Function● Can return multiple values● Unlike in C you can return address of a localvariable● Functions can be "attached" to a struct orinterfacefunc NewFile(fd int, name string) *File {if fd < 0 {return nil}f := File{fd, name, nil, 0}return &f}func (v Vertex)Print() string{}
  19. 19. Sample codepackage mainimport "fmt"// fib returns a function that returns successive Fibonacci numbers.func fib() func() int {a, b := 0, 1return func() int {a, b = b, a+breturn a}}func main() {f := fib()// Function calls are evaluated left-to-right.fmt.Println(f(), f(), f(), f(), f())}
  20. 20. Interface● Used to specify a behavior of an object● A type can implement multiple interfaces● Interfaces can be used in place of concretetypes● Empty interface is met by any typetype Stringer interface {ToString() string}
  21. 21. Embedding● a bit like inheritance● allows to combine structs or interfacestype Reader interface {Read(p []byte) (n int, err error)}type Writer interface {Write(p []byte) (n int, err error)}// ReadWriter is the interface that combines the Reader and Writer interfaces.type ReadWriter interface {ReaderWriter}
  22. 22. Channels and goroutines"Do not communicate by sharing memory;instead, share memory by communicating"● goroutine - is a lightweight concurrentfunction (like thread)● remove complexities of thread management● channels are used for communicatingbetween goroutines● they can be buffered or unbuffered
  23. 23. Example of using goroutines andchannelsfunc sum(a []int, c chan int) {sum := 0for _, v := range a {sum += v}c <- sum // send sum to c}func main() {a := []int{7, 2, 8, -9, 4, 0}c := make(chan int)go sum(a[:len(a)/2], c)go sum(a[len(a)/2:], c)x, y := <-c, <-c // receive from cfmt.Println(x, y, x+y)}
  24. 24. What is go good for?"large programs written by many developers,growing over time to support networkedservices in the cloud: in short, server software"-- Rob Pike
  25. 25. Resources● http://tour.golang.org● http://golangtutorials.blogspot.ie● http://golang.org/doc/effective_go.htm● http://www.golang-book.com● https://github.com/golang-samples

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