concurrent goroutines

gobyexample/channel-buffering.go

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	messages := make(chan string, 2)
+	messages <- "buffered"
+	messages <- "channel"
+
+	fmt.Println(<-messages)
+	fmt.Println(<-messages)
+}

gobyexample/channel-directions.go

@@ -0,0 +1,20 @@
+package main
+
+import "fmt"
+
+func ping(pings chan<- string, msg string) {
+	pings <- msg
+}
+
+func pong(pings <-chan string, pongs chan<- string) {
+	msg := <-pings
+	pongs <- msg
+}
+
+func main() {
+	pings := make(chan string, 1)
+	pongs := make(chan string, 1)
+	ping(pings, "passed message")
+	pong(pings, pongs)
+	fmt.Println(<-pongs)
+}

gobyexample/channel-synchronization.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func worker(done chan bool) {
+	fmt.Print("working...")
+	time.Sleep(time.Second)
+	fmt.Println("done")
+
+	done <- true
+}
+
+func main() {
+	done := make(chan bool, 1)
+	go worker(done)
+
+	<-done
+}

gobyexample/channels.go

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	messages := make(chan string)
+
+	go func() { messages <- "ping" }()
+
+	msg := <-messages
+	fmt.Println(msg)
+}

gobyexample/closures.go

@@ -0,0 +1,22 @@
+package main
+
+import "fmt"
+
+func intSeq() func() int {
+	i := 0
+	return func() int {
+		i++
+		return i
+	}
+}
+
+func main() {
+	nextInt := intSeq()
+
+	fmt.Println(nextInt())
+	fmt.Println(nextInt())
+	fmt.Println(nextInt())
+
+	newInts := intSeq()
+	fmt.Println(newInts())
+}

gobyexample/errors.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+func f1(arg int) (int, error) {
+	if arg == 42 {
+		return -1, errors.New("can't work with 42")
+	}
+	return arg + 3, nil
+}
+
+type argError struct {
+	arg int
+	prob string
+}
+
+func (e *argError) Error() string {
+	return fmt.Sprintf("%d - %s", e.arg, e.prob)
+}
+
+func f2(arg int) (int, error) {
+	if arg == 42 {
+		return -1, &argError{arg,  "can't work with it"}
+	}
+	return arg + 3, nil
+}
+
+func main() {
+	for _, i := range []int{7 ,42} {
+		if r, e := f1(i); e != nil {
+			fmt.Println("f1 failed:", e)
+		} else {
+			fmt.Println("f1 worked:", r)
+		}
+	}
+
+	for _, i := range []int{7, 42} {
+		if r,e := f2(i); e != nil {
+			fmt.Println("f2 failed:", e)
+		} else {
+			fmt.Println("f2 worked:", r)
+		}
+	}
+
+	_, e := f2(42)
+	if ae, ok := e.(*argError); ok {
+		fmt.Println(ae.arg)
+		fmt.Println(ae.prob)
+	}
+}

gobyexample/functions.go

@@ -0,0 +1,19 @@
+package main
+
+import "fmt"
+
+func plus(a int, b int) int {
+	return a+b
+}
+
+func plusPlus(a, b, c int) int {
+	return a + b + c
+}
+
+func main() {
+	res := plus(1, 2)
+	fmt.Println("1+2 =", res)
+	
+	res = plusPlus(1, 2, 3)
+	fmt.Println("1+2+3 =", res)
+}

gobyexample/goroutines.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func f(from string) {
+	for i := 0; i < 3; i++ {
+		fmt.Println(from, ":", i)
+	}
+}
+
+func main() {
+	f("direct")
+
+	go f("goroutine")
+
+	go func(msg string) {
+		fmt.Println(msg)
+	}("going")
+
+	time.Sleep(time.Second)
+	fmt.Println("done")
+}

gobyexample/interfaces.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+type geometry interface {
+	area() float64
+	perim() float64
+}
+
+type rect struct {
+	width, height float64
+}
+type circle struct {
+	radius float64
+}
+
+func (r *rect) area() float64 {
+	return r.width * r.height
+}
+func (r *rect) perim() float64 {
+	return 2*r.width + 2*r.height
+}
+
+func (c *circle) area() float64 {
+	return math.Pi * c.radius * c.radius
+}
+func (c *circle) perim() float64 {
+	return 2 * math.Pi * c.radius
+}
+
+func measure(g geometry) {
+	fmt.Println(g)
+	fmt.Println(g.area())
+	fmt.Println(g.perim())
+}
+
+func main() {
+	r := &rect{width:3, height:4}
+	c := &circle{radius: 5}
+
+	measure(r)
+	measure(c)
+}

gobyexample/methods.go

@@ -0,0 +1,26 @@
+package main
+
+import "fmt"
+
+type rect struct {
+	width, height int
+}
+
+func (r *rect) area() int {
+	return r.width * r.height
+}
+
+func (r rect) perim() int {
+	return 2*r.width + 2*r.height
+}
+
+func main() {
+	r := rect{width: 10, height: 5}
+
+	fmt.Println("area:", r.area())
+	fmt.Println("perim:", r.perim())
+
+	rp := &r
+	fmt.Println("area:", rp.area())
+	fmt.Println("perim:", rp.perim())
+}

gobyexample/multiple-return-values.go

@@ -0,0 +1,16 @@
+package main
+
+import "fmt"
+
+func  vals() (int, int) {
+	return 3,7
+}
+
+func main() {
+	a,b := vals()
+	fmt.Println(a)
+	fmt.Println(b)
+
+	_, c := vals()
+	fmt.Println(c)
+}

gobyexample/pointers.go

@@ -0,0 +1,24 @@
+package main
+
+import "fmt"
+
+func zeroval(ival int) {
+	ival = 0
+}
+
+func zeroptr(iptr *int) {
+	*iptr = 0
+}
+
+func main() {
+	i := 1
+	fmt.Println("initial:", i)
+
+	zeroval(i)
+	fmt.Println("zeroval:", i)
+
+	zeroptr(&i)
+	fmt.Println("zeroptr:", i)
+
+	fmt.Println("pointer:", &i)
+}

gobyexample/range.go

@@ -0,0 +1,31 @@
+package main
+
+import "fmt"
+
+func main() {
+	nums := []int{2, 3, 4}
+	sum := 0
+	for _, num := range nums {
+		sum += num
+	}
+	fmt.Println("sum:",sum)
+
+	for i,num := range nums {
+		if num == 3 {
+			fmt.Println("index:",i)
+		}
+	}
+
+	kvs := map[string]string{"a":"apple", "b":"banana"}
+	for k, v := range kvs {
+		fmt.Printf("%s -> %s\n", k, v)
+	}
+	
+	for k := range kvs {
+		fmt.Println("key:", k)
+	}
+
+	for i,c := range "go" {
+		fmt.Println(i,c)
+	}
+}

gobyexample/recursion.go

@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+func fact(n int) int {
+	if n==0 {
+		return 1
+	}
+	return n * fact(n-1)
+}
+
+func main() {
+	fmt.Println(fact(7))
+
+	var fib func(n int) int
+
+	fib = func(n int) int {
+		if n<2 {
+			return n
+		}
+		return fib(n-1) + fib(n-2)
+	}
+
+	fmt.Println(fib(7))
+}

gobyexample/select.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func main() {
+	c1 := make(chan string)
+	c2 := make(chan string)
+
+	go func() {
+		time.Sleep(1 * time.Second)
+		c1 <- "one"
+	}()
+
+	go func() {
+		time.Sleep(2 * time.Second)
+		c1 <- "two"
+	}()
+
+	for i := 0; i < 2; i++ {
+		select {
+			case msg1 := <-c1:
+				fmt.Println("received", msg1)
+			case msg2 := <-c2:
+				fmt.Println("received", msg2)
+		}
+	}
+}

gobyexample/structs.go

@@ -0,0 +1,38 @@
+package main
+
+import "fmt"
+
+type person struct {
+	name string
+	age int
+}
+
+func newPerson(name string) *person {
+	p := person{name:name}
+	p.age = 42
+	return &p
+}
+
+
+func main() {
+
+	fmt.Println(person{"Bob", 20})
+
+	fmt.Println(person{name:"Alice", age:30})
+
+	fmt.Println(person{name:"Fred"})
+
+	fmt.Println(&person{name: "Ann", age: 40})
+
+	fmt.Println(newPerson("Jon"))
+
+	s := person{name:"Sean", age: 50}
+	fmt.Println(s.name)
+
+	sp := &s
+	fmt.Println(sp.age)
+
+	sp.age = 51
+	fmt.Println(sp.age)
+
+}

gobyexample/variadic-functions.go

@@ -0,0 +1,20 @@
+package main
+
+import "fmt"
+
+func sum(nums ...int) {
+	fmt.Print(nums, " ")
+	total := 0
+	for _, num := range nums {
+		total += num
+	}
+	fmt.Println(total)
+}
+
+func main() {
+	sum(1,2)
+	sum(1,2,3)
+
+	nums := []int{1, 2, 3, 4}
+	sum(nums...)
+}

gobyexample/waitgroups.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+	"time"
+)
+
+func worker(id int) {
+	fmt.Printf("Worker %d starting\n", id)
+	time.Sleep(time.Second)
+	fmt.Printf("Worker %d done\n", id)
+}
+
+func main() {
+	var wg sync.WaitGroup
+
+	for i:= 1; i<=5; i++ {
+		wg.Add(1)
+
+		i := i
+
+		go func() {
+			defer wg.Done()
+			worker(i)
+		}()
+	}
+	wg.Wait()
+}

hello/hello.go

@@ -1,7 +1,11 @@
 package main
 
-import "fmt"
+import (
+        "fmt"
+        "c.infdj.com/GO/courses_golang/hello/morestrings"
+)
 
 func main() {
-	fmt.Println("Hello, world.")
+        // fmt.Println("Hello, world.")
+        fmt.Println(morestrings.ReverseRunes("!oG ,olleH"))
 }

hello/morestrings/reverse.go

@@ -0,0 +1,12 @@
+// Package morestrings implements additional functions to manipulate UTF-8
+// encoded strings, beyond what is provided in the standard "strings" package.
+package morestrings
+
+// ReverseRunes returns its argument string reversed rune-wise left to right.
+func ReverseRunes(s string) string {
+	r := []rune(s)
+	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+		r[i], r[j] = r[j], r[i]
+	}
+	return string(r)
+}

hello/morestrings/reverse_test.go

@@ -0,0 +1,19 @@
+package morestrings
+
+import "testing"
+
+func TestReverseRunes(t *testing.T) {
+	cases := []struct {
+		in, want string
+	}{
+		{"Hello, world", "dlrow ,olleH"},
+		{"Hello, 世界", "界世 ,olleH"},
+		{"", ""},
+	}
+	for _, c := range cases {
+		got := ReverseRunes(c.in)
+		if got != c.want {
+			t.Errorf("ReverseRunes(%q) == %q, want %q", c.in, got, c.want)
+		}
+	}
+}