2015

2015/02-devconf.cz/talk.slide

@@ -0,0 +1,170 @@
+Golang - the good, the bad, the ugly
+06 Feb 2015 - devconf.cz
+
+Vincent Batts
+Developer
+@vbatts
+vbatts@redhat.com
+
+* howdy
+
+$> whoami
+vbatts
+$> id -Gn
+vbatts devel openshift docker
+
+* golang
+
+## Notes
+# - libraries - source only, but can link to C *.so and *.a
+# - Fork/Exec are coupled together (for coroutine and GC reasons)
+# - Threading, and multiproc, concurrent logic
+#  -- nice and easy to use
+#  -- Make for tricky handling of C calls (i.e. setns)
+# - `go get` is handy
+# - cross-compile without hardly any bootstrapping
+#  -- native compiler supported arches
+#  -- gccgo works for the arch gcc is compiled for
+# - primitives can seem a bit magical
+#  -- conditional returns
+#  -- for ... range
+#  -- iota
+# - no ifdefs, but build tags
+# - error handling, rather than exception catching
+
+* 
+
+.image ./gopher.png
+
+* Overview
+
+- strongly typed
+- compiled
+- stylistically nice
+- opinionated
+
+* Good
+
+* 
+
+.image ./rainbow.jpg
+
+* fully qualified imports
+
+.code ./talk/imports.go /START1/,/STOP1/
+
+* fast compiles
+
+(Perhaps other compilers are slow)
+
+.play ./talk/hello.go /START1/,/STOP1/
+
+* defer
+
+.code ./talk/good0.go /START1/,/STOP1/
+
+* Garbage Collected
+
+- Super convenient
+- references
+- completed goroutines
+
+* simple exports
+
+.code ./talk/good1.go /START1/,/STOP1/
+
+* concurrency
+
+.play ./talk/pingpong.go /STARTMAIN1/,/STOPMAIN1/
+.link http://talks.golang.org/2013/advconc.slide Sameer Ajmani - Advanced Concurrency
+
+* 
+.image ./kanye_imma_bookmarklet.png 320 _
+
+- easy learning curve
+- `go get`
+- cross-compiles
+
+
+* Bad
+
+* 
+
+# they come along, and affect how you do your work
+.image ./cats20.gif
+
+* lack of generics?
+# i don't feel strongly about this, though many do
+- interfaces - are enough for most
+- go1.4 introduced go:generate
+# produce code for Set, Graph etc, for the types needed, but at compile time. No need to reflect.
+
+* Debugging
+
+- gdb is there, sort of
+- some known debugging tools for ELF are not useful
+- fmt.Printf("%#v\n", ...)
+
+* Concurrency and GC
+
+Calls like setns(2) are rough
+
+
+(yes, even with runtime.LockOSThread())
+
+* Fork/Exec
+
+Not Separate, but together
+
+* Ugly? (maybe just new)
+
+* 
+.image ./revenge-of-the-nerds-o.gif
+
+* build tags
+
+.code ./talk/tags.go /START1/,/STOP1/
+
+or files with *_linux.go like suffix
+
+* _
+
+bit bucket
+
+* channels
+
+.play ./talk/ugly0.go /START1/,/STOP1/
+
+* iota
+
+.code ./talk/ugly1.go /START1/,/STOP1/
+
+* for range
+
+array (or string)
+
+.play ./talk/primitive1.go /START1/,/STOP1/
+
+* for range
+
+map
+
+.play ./talk/primitive2.go /START1/,/STOP1/
+
+* for range
+
+channel (like an iterator)
+
+.play ./talk/primitive3.go /START1/,/STOP1/
+
+* for range
+
+channel
+
+.code ./talk/primitive3.go /START2/,/STOP2/
+
+* Conclusions?
+
+* use-case
+
+- like all languages, align with you use-case

2015/02-devconf.cz/talk/good0.go

@@ -0,0 +1,48 @@
+// +build ignore
+
+package main
+
+import (
+	"compress/gzip"
+	"encoding/json"
+	"flag"
+	"io/ioutil"
+	"log"
+	"os"
+)
+
+func main() {
+	for _, arg := range flag.Args() {
+		func() {
+			// START1 OMIT
+			fh, err := os.Open(arg)
+			if err != nil {
+				log.Fatal(err)
+			}
+			defer fh.Close()
+
+			gz, err := gzip.NewReader(fh)
+			if err != nil {
+				log.Fatal(err)
+			}
+			defer gz.Close()
+
+			buf, err := ioutil.ReadAll(gz)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			var mine MyStruct
+			err = json.Unmarshal(&mine)
+			if err != nil {
+				log.Fatal(err)
+			}
+			// STOP1 OMIT
+
+		}()
+	}
+
+}
+
+type MyStruct struct {
+}

2015/02-devconf.cz/talk/good1.go

@@ -0,0 +1,20 @@
+// +build ignore
+
+package main
+
+// START1 OMIT
+// exported
+type Foo struct {
+	Bar string // exported
+	baz bool   // private
+}
+
+// private
+type bif struct {
+	Harf, Buz int64 // doesn't matter
+}
+
+// STOP1 OMIT
+
+func main() {
+}

2015/02-devconf.cz/talk/hello.go

@@ -0,0 +1,10 @@
+// +build ignore
+
+// START1 OMIT
+package main
+
+func main() {
+	println("Howdy y'all")
+}
+
+// STOP1 OMIT

2015/02-devconf.cz/talk/imports.go

@@ -0,0 +1,18 @@
+// +build ignore
+
+package main
+
+// START1 OMIT
+import (
+	"fmt"
+	"os"
+
+	"github.com/foo/bar"
+)
+
+// STOP1 OMIT
+
+func main() {
+	fmt.Println(bar.Baz())
+	_ = os.FileInfo
+}

2015/02-devconf.cz/talk/pingpong.go

@@ -0,0 +1,33 @@
+// +build OMIT
+
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+// STARTMAIN1 OMIT
+type Ball struct{ hits int }
+
+func main() {
+	table := make(chan *Ball)
+	go player("ping", table)
+	go player("pong", table)
+
+	table <- new(Ball) // game on; toss the ball
+	time.Sleep(1 * time.Second)
+	<-table // game over; grab the ball
+}
+
+func player(name string, table chan *Ball) {
+	for {
+		ball := <-table
+		ball.hits++
+		fmt.Println(name, ball.hits)
+		time.Sleep(100 * time.Millisecond)
+		table <- ball
+	}
+}
+
+// STOPMAIN1 OMIT

2015/02-devconf.cz/talk/primitive1.go

@@ -0,0 +1,25 @@
+// +build ignore
+
+package main
+
+import "fmt"
+
+func main() {
+	// START1 OMIT
+	names := []string{
+		"Michael",
+		"Jan",
+		"Sean",
+		"Silvia",
+	}
+	for i, name := range names {
+		fmt.Printf("%q is the %d name\n", name, i)
+	}
+	for i := range names {
+		fmt.Printf("%q is the %d name\n", names[i], i)
+	}
+	for _, name := range names {
+		fmt.Printf("%q is the ... name\n", name)
+	}
+	// STOP1 OMIT
+}

2015/02-devconf.cz/talk/primitive2.go

@@ -0,0 +1,56 @@
+// +build ignore
+
+package main
+
+import "fmt"
+
+func main() {
+	// START1 OMIT
+	infos := map[string]Info{
+		"Michael": Info{
+			City:   "Happyville",
+			Status: Open,
+		},
+		"Jan": Info{
+			City:   "Confusville",
+			Status: Closed,
+		},
+		"Sean": Info{
+			City:   "Septober",
+			Status: Complicated,
+		},
+		"Silvia": Info{
+			City:   "Curiousville",
+			Status: Curios,
+		},
+	}
+	for name, info := range infos {
+		fmt.Printf("%q is %s in %q\n", name, info.Status, info.City)
+	}
+	// STOP1 OMIT
+}
+
+type Info struct {
+	City   string
+	Status Status
+}
+type Status int
+
+var (
+	Open        = Status(0)
+	Closed      = Status(1)
+	Complicated = Status(2)
+	Curios      = Status(3)
+)
+
+func (s Status) String() string {
+	switch s {
+	case Open:
+		return "open"
+	case Closed:
+		return "closed"
+	case Complicated:
+		return "complicated"
+	}
+	return "hurr"
+}

2015/02-devconf.cz/talk/primitive3.go

@@ -0,0 +1,37 @@
+// +build ignore
+
+package main
+
+import "fmt"
+
+func main() {
+	// START1 OMIT
+	fmt.Println("I've got:")
+	for card := range ReadEmAndWeep() {
+		fmt.Printf(" %s of %s\n", card.Value, card.Suite)
+	}
+	// STOP1 OMIT
+}
+
+type Card struct {
+	Suite, Value string
+}
+
+// START2 OMIT
+func ReadEmAndWeep() <-chan Card {
+	c := make(chan Card)
+	go func() {
+		for _, card := range []Card{
+			Card{"Ace", "Jack"},
+			Card{"Ace", "Queen"},
+			Card{"Ace", "King"},
+			Card{"Ace", "Ace"},
+		} {
+			c <- card
+		}
+		close(c)
+	}()
+	return c
+}
+
+// STOP2 OMIT

2015/02-devconf.cz/talk/tags.go

@@ -0,0 +1,8 @@
+// START1 OMIT
+// +build !windows linux,cgo
+// STOP1 OMIT
+
+package main
+
+func main() {
+}

2015/02-devconf.cz/talk/ugly0.go

@@ -0,0 +1,16 @@
+// +build ignore
+
+package main
+
+func main() {
+	// START1 OMIT
+	c := make(chan int)
+	go func() {
+		for i := 0; i < 10; i++ {
+			c <- i
+		}
+		close(c)
+	}()
+	println(<-c)
+	// STOP1 OMIT
+}

2015/02-devconf.cz/talk/ugly1.go

@@ -0,0 +1,22 @@
+// +build ignore
+
+package main
+
+// START1 OMIT
+const (
+	DeviceCreate TaskType = iota
+	DeviceReload
+	DeviceRemove
+	DeviceRemoveAll
+	DeviceSuspend
+	DeviceResume
+	DeviceInfo
+	DeviceDeps
+)
+
+// STOP1 OMIT
+
+type TaskType int
+
+func main() {
+}