Cut. it s not just for Google. Eleanor McHugh.

Size: px

Start display at page:

Download "Cut. it s not just for Google. Eleanor McHugh."

Brooke Dalton
6 years ago
Views:

1 Ro u gh Cut! Go it s not just for Google Eleanor McHugh

2 compiled

3 garbage collected

4 imperative

5 package main import fmt const HELLO string = hello var WORLD string = world func main() { fmt.println(hello, WORLD)

6 strongly typed

7 boolean, numeric, array value structure, interface reference pointer, slice, string, map, channel function function, method, closure

8 underlying type method set expressed type

9 underlying type method set expressed type embedded types

10 package Integer type Int int func (i *Int) Add(x int) { *i += Int(x)

11 type Buffer []Int func (b Buffer) Swap(i, j int) { b[i], b[j] = b[j], b[i] func (b Buffer) Clone() Buffer { s := make(buffer, len(b)) copy(s, b) return s func (b Buffer) Move(i, n int) { if n > len(b) - i { n = len(b) - i segment_to_move := b[:i].clone() copy(b, b[i:i + n]) copy(b[n:i + n], segment_to_move)

12 package main import fmt import "Integer" func main() { i := Integer.Buffer{0, 1, 2, 3, 4, 5 b := i.clone() b.swap(1, 2) b.move(3, 2) b[0].add(3) fmt.printf( b[0:2] = %v\n, b[0:2]) produces: b[0:2] = [6 4]

13 testable

14 func (b Buffer) Eq(o Buffer) (r bool) { if len(b) == len(o) { for i := len(b) - 1; i > 0; i-- { if b[i]!= o[i] { return r = true return

15 func TestSwap(t *testing.t) { i := Buffer{0, 1, 2, 3, 4, 5 b := i.clone() b.swap(1, 2) if!b[1:3].eq(buffer{2, 1) { t.fatalf("b = %v", b)

16 package Vector import. "Integer" type Vector struct { Buffer func (v *Vector) Clone() *Vector { return &Vector{v.Buffer.Clone() func (v *Vector) Slice(i, j int) Buffer { return v.buffer[i:j]

17 package Vector import "testing" func TestVectorSwap(t *testing.t) { i := Vector{Buffer{0, 1, 2, 3, 4, 5 v := i.clone() v.swap(1, 2) r := Vector{Buffer{0, 2, 1, 3, 4, 5 switch { case!v.eq(r.buffer): fallthrough case!v.buffer.eq(r.buffer): t.fatalf("b[0:5] = %v", v)

18 include $(GOROOT)/src/Make.inc TARG=integer GOFILES=\ integer.go\ vector.go include $(GOROOT)/src/Make.pkg

19 func BenchmarkVectorClone6(b *testing.b) { v := Vector{Buffer{0, 1, 2, 3, 4, 5 for i := 0; i < b.n; i++ { _ = v.clone() func BenchmarkVectorSwap(b *testing.b) { b.stoptimer() v := Vector{Buffer{0, 1, 2, 3, 4, 5 b.starttimer() for i := 0; i < b.n; i++ { v.swap(1, 2)

20 $ gotest -bench="benchmark" rm -f _test/scripts.a 6g -o _gotest_.6 integer.go vector.go nominal_typing_test.go embedded_typing_benchmark_test.go embedded_typing_test.go rm -f _test/scripts.a gopack grc _test/scripts.a _gotest_.6 PASS integer.benchmarkvectorswap ns/op integer.benchmarkvectorclone ns/op

21 dynamic

22 type Adder interface { Add(j int) Subtract(j int) Result() interface{ Reset()

23 type IAdder int func (i IAdder) Add(j int) { i[0] += i[j] func (i IAdder) Subtract(j int) { i[0] -= i[j] func (i IAdder) Result() interface{ { return i[0] func (i IAdder) Reset() { i[0] = *new(int)

24 type FAdder []float32 func (f FAdder) Add(j int) { f[0] += f[j] func (f FAdder) Subtract(j int) { f[0] -= f[j] func (f FAdder) Result() interface{ { return f[0]

25 func TestAdder(t *testing.t) { var a Adder a = IAdder{0, 1, 2 a.add(1) if i.result().(int)!= 1 { t.fatalf("iadder::add(1) %v!= %v", a.result(), 1) a.subtract(2) if a.result().(int)!= -1 { t.fatalf("iadder::subtract(2) %v!= %v", a.result()), -1 a = FAdder{0.0, 1.0, 2.0 a.add(1) if a.result().(float32)!= 1.0 { t.fatalf("fadder::add(1) %v!= %v", a.result(), 1.0)

26 reflected

27 package generalise import "reflect" func Allocate(i interface{, limit... int) (n interface{) { switch v := reflect.valueof(i); v.kind() { case reflect.slice: l := v.cap() if len(limit) > 0 { l = limit[0] n = reflect.makeslice(v.type(), l, l).interface() case reflect.map: return n = reflect.makemap(v.type()).interface()

28 package generalise import. "reflect" func Allocate(i interface{, limit... int) (n interface{) { switch v := ValueOf(i); v.kind() { case Slice: l := v.cap() if len(limit) > 0 { l = limit[0] n = MakeSlice(v.Type(), l, l).interface() case Map: return n = MakeMap(v.Type()).Interface()

29 func throwspanic(f func()) (b bool) { defer func() { if x := recover(); x!= nil { b = true () f() return

30 func TestAllocate(t *testing.t) { var s2 []int s1 := []int{0, 1, 2 m := map[int] int{1: 1, 2: 2, 3: 3 switch { case throwspanic(func() { s2 = Allocate(s1, 1).([]int) ): t.fatal("unable to allocate new slice") case len(s2)!= 1 cap(s2)!= 1: t.fatal("new slice should be %v not %v", make([]int, 0, 1), s2) case throwspanic(func() { Allocate(m) ): t.fatal("unable to allocate new map")

31 func Duplicate(i interface{) (clone interface{) { if clone = Allocate(i); clone!= nil { switch clone := ValueOf(clone); clone.kind() { case Slice: Copy(clone, ValueOf(i)) case Map: return m := ValueOf(i) for _, k := range m.keys() { clone.setmapindex(k, m.mapindex(k))

32 func TestDuplicateSlice(t *testing.t) { s1 := []int{0, 1, 2 var s2 []int if throwspanic(func() { s2 = Duplicate(s1).([]int) ) { t.fatalf("unable to duplicate slice %v\n", s1) switch { case len(s1)!= len(s2): fallthrough case cap(s1)!= cap(s2): fallthrough case s1[0]!= s2[0]: fallthrough case s1[1]!= s2[1]: fallthrough case s1[2]!= s2[2]: fallthrough t.fatalf("duplicating %v produced %v", s1, s2)

33 func TestDuplicateMap(t *testing.t) { m1 := map[int]int{1: 1, 2: 2, 3: 3 var m2 map[int]int if throwspanic(func() { m2 = Duplicate(m1).(map[int]int) ) { t.fatalf("unable to duplicate map %v\n", m1) switch { case len(m1)!= len(m2): fallthrough case m1[1]!= m2[1]: fallthrough case m1[2]!= m2[2]: fallthrough case m1[3]!= m2[3]: fallthrough t.fatalf("duplicating %v produced %v", m1, m2)

34 low-level

35 package raw import. "reflect" import "unsafe" var _BYTE_SLICE Type = Typeof([]byte(nil)) type MemoryBlock interface { ByteSlice() []byte func valueheader(v reflect.value) (Header *reflect.sliceheader) { if v.isvalid() { s := int(v.type().size()) header = &reflect.sliceheader{ v.unsafeaddr(), s, s return

36 func SliceHeader(i interface{) (Header *SliceHeader, Size, Align int) { switch value := Indirect(ValueOf(i)); value.kind() { case Slice: Header = (*SliceHeader)(unsafe.Pointer(value.UnsafeAddr())) t := value.type().elem() Size = int(t.size()) Align = t.align() case Interface: Header, Size, Align = SliceHeader(value.Elem()) return func Scale(oldHeader *SliceHeader, oldesize, newesize int) (h *SliceHeader) { if oldheader!= nil { s := float64(oldesize) / float64(newesize) h = &SliceHeader{ Data: oldheader.data h.len = int(float64(oldheader.len) * s) h.cap = int(float64(oldheader.cap) * s) return

37 func ByteSlice(i interface{) []byte { switch i := i.(type) { case []byte: return i case MemoryBlock: return i.byteslice() var header *SliceHeader switch v := ValueOf(i); value.kind() { case Interface, Ptr: header = valueheader(v.elem()) case Slice: h, s, _ := SliceHeader(i) header = Scale(h, s, 1) case String: s := v.get() h := *(*StringHeader)(unsafe.Pointer(&s)) header = &SliceHeader{ h.data, h.len, h.len default: header = valueheader(v) return unsafe.unreflect(_byte_slice, unsafe.pointer(header)).([]byte)

38 concurrent

39 package main import "fmt" func main() { var c chan int c = make(chan int) limit := 16 go func() { for i := limit; i > 0; i-- { fmt.print(<-c) () for i := limit; i > 0; i-- { select { case c <- 0: case c <- 1: produces:

40 func main() { var c chan int c = make(chan int, 16) go func() { for i := 16; i > 0; i-- { fmt.print(<-c) () go func() { select { case c <- 0: case c <- 1: () for { produces:

41 package generalise type SignalSource func(status chan bool) func Wait(s SignalSource) { done := make(chan bool) defer close(done) go s(done) <-done func WaitAll(count int, s SignalSource) { done := make(chan bool) defer close(done) go s(done) for i := 0; i < count; i++ { <- done

42 type Iteration func(k, x interface{) bool func (i Iteration) apply(k, v interface{, c chan bool) { go func() { c <-i(k, v) () func (f Iteration) Each(c interface{) { switch c := ValueOf(c); c.kind() { case Slice: WaitAll(c.Len(), SignalSource(func(done chan bool) { for i := 0; i < c.len(); i++ { f.apply(i, c.elem(i).interface(), done) )) case Map: WaitAll(c.Len(), SignalSource(func(done chan bool) { for _, k := range c.keys() { f.apply(k, c.elem(k).interface(), done) ))

43 type Results chan interface{ type Combination func(x, y interface{) interface{ func (f Combination) Reduce(c, s interface{) (r Results) { r = make(results) go func() { Iteration(func(k, x interface{) (ok bool) { s = f(s, x) return true ).Each(c) r <- s () return

44 type Transformation func(x interface{) interface{ func (t Transformation) Transform(x interface{) Value { return ValueOf(t(x)) func (t Transformation) Map(c interface{) (r interface{) { r = Allocate(c) if i := MapIterator(r); i!= nil { i.each(c) return

45 func MapIterator(c interface{) (i Iteration) { switch n := ValueOf(c); n.kind() { case Slice: i = Iteration(func(k, x interface{) bool { n.elem(k.(int)).setvalue(t.getvalue(x)) return true ) case Map: return i = Iteration(func(k, x interface{) bool { n.setmapindex(valueof(k), t.getvalue(x)) return true )

46 func main() { s := []int{0, 1, 2, 3, 4, 5 d := Transformation(func(x interface{) interface{ { return x.(int) * 2 ).Map(s) sum := Combination(func(x, y interface{) interface{ { return x.(int) + y.(int) ) fmt.printf("s = %v, sum = %v\n", s, (<- sum.reduce(s, 0)).(int)) fmt.printf("d = %v, sum = %v\n", d, (<- sum.reduce(d, 0)).(int)) produces: s = [ ], sum = 15 d = [ ], sum = 30

47 extensible

48 include $(GOROOT)/src/Make.inc TARG=sqlite3 CGOFILES=\ sqlite3.go\ database.go ifeq ($(GOOS),darwin) CGO_LDFLAGS=/usr/lib/libsqlite3.0.dylib else CGO_LDFLAGS=-lsqlite3 endif include $(GOROOT)/src/Make.pkg

49 package sqlite3 // #include <sqlite3.h> import "C" import "fmt" import "os" type Database struct { handle Filename Flags *C.sqlite3 string C.int func (db *Database) Error() os.error { return Errno(C.sqlite3_errcode(db.handle))

50 const( OK = Errno(iota) ERROR CANTOPEN = Errno(14) ) var errtext = map[errno]string { ERROR: "SQL error or missing database", CANTOPEN: "Unable to open the database file", type Errno int func (e Errno) String() (err string) { if err = errtext[e]; err == "" { err = fmt.sprintf("errno %v", int(e)) return

51 func (db *Database) Open(flags... int) (e os.error) { db.flags = 0 for _, v := range flags { db.flags = db.flags C.int(v) f := C.CString(db.Filename) if err := Errno(C.sqlite3_open_v2(f, &db.handle, db.flags, nil)); err!= OK { e = err else if db.handle == nil { e = CANTOPEN return func (db *Database) Close() { C.sqlite3_close(db.handle) db.handle = nil

52 func Open(filename string, flags... int) (db *Database, e os.error) { defer func() { if x := recover(); x!= nil { db.close() db = nil e = ERROR () db = &Database{ Filename: filename if len(flags) == 0 { e = db.open( C.SQLITE_OPEN_FULLMUTEX, C.SQLITE_OPEN_READWRITE, C.SQLITE_OPEN_CREATE ) else { e = db.open(flags...) return

53 fun!

54 finding out more twitter://#golightly wikipedia or google

Go Cheat Sheet. Operators. Go in a Nutshell. Declarations. Basic Syntax. Hello World. Functions. Comparison. Arithmetic. Credits

Go Cheat Sheet. Operators. Go in a Nutshell. Declarations. Basic Syntax. Hello World. Functions. Comparison. Arithmetic. Credits Credits Go Cheat Sheet Most example code taken from A Tour of Go, which is an excellent introduction to Go. If you're new to Go, do that tour. Seriously. Original HTML Cheat Sheet by Ariel Mashraki (a8m):