Go

Hello World

package main

import "fmt"

func main() {
    fmt.Printf("Hello World")
}

Hello World

Functions

package main

import "fmt"

func add(x, y int) int {
    return x + y
}

func main() {
    fmt.Println(add(42, 13))
}
package main

import "fmt"

func add(x int, y int) int {
    return x + y
}

func main() {
    fmt.Println(add(42, 13))
}

Hello World

Functions ( cont. )

package main

import "fmt"

func swap(x, y string) (string, string) {
    return y, x
}

func main() {
    a, b := swap("hello", "world")
    fmt.Println(a, b)
}

Hello World

Named return values

package main

import "fmt"

func split(sum int) (x, y int) {
    x = sum * 4 / 9
    y = sum - x
    return
}

func main() {
    fmt.Println(split(17))
}

Hello World

Variables

package main

import "fmt"

var x, y int = 1, 2

func main() {
    var c, python, java = true, false, "pls no!"
    fmt.Println(x, y, c, python, java)
}

Hello World

Variables ( cont. )

package main

import "fmt"

func main() {
    c, python, java := true, false, "pls no!"
    var x, y int = 1, 2

    k := 3
    fmt.Println(x, y, k, c, python, java)
}
package main

import "fmt"
var (
    c bool = true
    python bool = false
    java string = "pls no!"
)

func main() {
    var x, y int = 1, 2

    k := 3
    fmt.Println(x, y, k, c, python, java)
}

Hello World 

Basic Types

bool

string

int  int8  int16  int32  int64
uint uint8 uint16 uint32 uint64

byte // alias for uint8

rune // alias for int32  ( unicode )

float32 float64

complex64 complex128

Hello World 

Default Values

package main

import "fmt"

func main() {
    var i int
    var f float64
    var b bool
    var s string
    fmt.Printf("%v %v %v %q\n", i, f, b, s)
}
0 0 false ""

Hello World 

For

package main

import "fmt"

func main() {
    sum := 0
    for i := 0; i < 10; i++ {
    	sum += i
    }
    fmt.Println(sum)
}

Hello World 

For ( cont.)

package main

import "fmt"

func main() {
    sum := 1
    for ; sum < 1000; {
	sum += sum
    }
    fmt.Println(sum)
}

Hello World 

"While" is spelt "For" in go.

package main

import "fmt"

func main() {
    sum := 1
    for sum < 1000 {
	sum += sum
    }
    fmt.Println(sum)
}

Hello World 

Forever

package main

func main() {
    for {

    }
}

Hello World 

If

package main

import "fmt"

func add(x, y int) int {
    if x < 4 {
        return x + y
    } else {
        return x - y
    }
    
}

Hello World 

Switch

package main

import (
    "fmt"
    "runtime"
)

func main() {
    fmt.Print("Go runs on ")
    os := runtime.GOOS
    switch os {
    case "darwin":
        fmt.Println("OS X.")
    case "linux":
        fmt.Println("Linux.")
        fmt.Printf("%s.", os)
    }
}

Hello World 

Variadic functions

func sum(nums ...int) {
    fmt.Print(nums, " ")
    total := 0
    for _, num := range nums {
        total += num
    }
    fmt.Println(total)
}

Channels

 typed pipes

Send v to channel ch

ch <- v

Receive from ch and assign to v 

v := <-ch

Practical (ish) Example

package main

import "fmt"

func add(x, y int, ch chan int) {

    ch <- x + y
}

func main() {
    
    ch := make(chan int)

    go add(5, 6, ch)
    go add(15, 3, ch)
    q, z := <- ch, <- ch

    fmt.Println(q, z, q+z)
}

Buffered Example

package main

import "fmt"

func main() {


    messages := make(chan string, 2)

    // Because this channel is buffered, we can send these
    // values into the channel without a corresponding
    // concurrent receive.
    messages <- "buffered"
    messages <- "channel"

    // Later we can receive these two values as usual.
    fmt.Println(<-messages)
    fmt.Println(<-messages)
}

Synchonization

package main

import "fmt"
import "time"


func worker(done chan bool) {
    fmt.Print("working...")
    time.Sleep(time.Second)
    fmt.Println("done")

    // Send a value to notify that we're done.
    done <- true
}

func main() {

    // Start a worker goroutine, giving it the channel to
    // notify on.
    done := make(chan bool, 1)
    go worker(done)

    // Block until we receive a notification from the
    // worker on the channel.
    <-done
}

Range

package main

import (
    "fmt"
)

func fibonacci(n int, c chan int) {
    x, y := 0, 1
    for i := 0; i < n; i++ {
        c <- x
        x, y = y, x+y
    }
    close(c)
}

func main() {
    c := make(chan int, 10)
    go fibonacci(15, c)
    for i := range c {
        fmt.Println(i)
    }
}

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