Update first lecture

This commit is contained in:
Fedor Korotkiy 2020-02-13 14:45:11 +03:00
parent 4006009c2c
commit 1f1c1870c6
9 changed files with 334 additions and 0 deletions

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lectures/00-intro/book.jpg Normal file

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package main
import (
"fmt"
"log"
"net/http"
"sync"
)
var (
counter int
mu sync.Mutex
)
func main() {
http.HandleFunc("/", handler)
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
func handler(w http.ResponseWriter, r *http.Request) {
var i int
mu.Lock()
i = counter
counter++
mu.Unlock()
fmt.Fprintf(w, "counter = %d\n", i)
}

22
lectures/00-intro/dup.go Normal file
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package main
import (
"bufio"
"fmt"
"os"
)
func main() {
counts := make(map[string]int)
input := bufio.NewScanner(os.Stdin)
for input.Scan() {
counts[input.Text()]++
}
// NOTE: ignoring potential errors from input.Err()
for line, n := range counts {
if n > 1 {
fmt.Printf("%d\t%s\n", n, line)
}
}
}

15
lectures/00-intro/echo.go Normal file
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package main
import (
"fmt"
"os"
)
func main() {
var s, sep string
for i := 1; i < len(os.Args); i++ {
s += sep + os.Args[i]
sep = " "
}
fmt.Println(s)
}

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@ -0,0 +1,15 @@
package main
import (
"fmt"
"os"
)
func main() {
s, sep := "", ""
for _, arg := range os.Args[1:] {
s += sep + arg
sep = " "
}
fmt.Println(s)
}

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package main
import (
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"time"
)
func main() {
start := time.Now()
ch := make(chan string)
for _, url := range os.Args[1:] {
go fetch(url, ch) // start a goroutine
}
for range os.Args[1:] {
fmt.Println(<-ch) // receive from channel ch
}
fmt.Printf("%.2fs elapsed\n", time.Since(start).Seconds())
}
func fetch(url string, ch chan<- string) {
start := time.Now()
resp, err := http.Get(url)
if err != nil {
ch <- fmt.Sprint(err) // send to channel ch
return
}
defer resp.Body.Close() // don't leak resources
nbytes, err := io.Copy(ioutil.Discard, resp.Body)
if err != nil {
ch <- fmt.Sprintf("while reading %s: %v", url, err)
return
}
secs := time.Since(start).Seconds()
ch <- fmt.Sprintf("%.2fs %7d %s", secs, nbytes, url)
}

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@ -79,3 +79,174 @@ Language
Простой синтаксис (понятный для людей *и* машин).
Простая система типов. Объектно ориентированный, но без иерархий.
* Hello World
.play -edit helloworld.go
: Как запустить. В презентации и в CLI.
: Что такое пакет.
: Импорты. fmt - стандартная библиотека.
: Пакет main.
: Автоматическое форматирование.
: goimports
* echo
.play -edit echo.go
: Слайсы. s[n:m], s[i], len(s).
: var создаёт переменную. Инициализация zero value.
* For loop
Полная форма.
for initialization; condition; post {
// statements
}
Как while.
for condition {
// statements
}
Бесконечный цикл.
for {
// statements
}
* echo2
.play -edit echo2.go
* Range
Полная форма.
for i, v := range slice {
// ...
}
Только индекс.
for i := range slice {
// ...
}
Индекс не используется.
for _, v := range slice {
// ...
}
* Переменные
s := ""
var s string
var s = ""
var s string = ""
* dup
.play -edit dup.go
: map. Создаётся через make(). Значения инициализируются нулём. Ключ должен иметь ==.
: Итерация по map.
: bufio.Scanner.
: Printf.
* Printf
%d decimal integer
%x, %o, %b integer in hexade cimal, octal, binary
%f, %g, %e floating-point number: 3.141593 3.141592653589793 3.141593e+00
%t boolean: true or false
%c rune (Unicode code point)
%s string
%q quoted string "abc" or rune 'c'
%v any value in a natural format
%T type of any value
%% literal percent sign (no operand)
Функции форматирования заканчиваются на `f`. `fmt.Errorf`, `log.Printf`.
* urlfetch
.code urlfetch.go /func main/,/^}/
* fetchall
.code fetchall.go /func main/,/^}/
* fetchall
.code fetchall.go /func fetch/,/^}/
* webserver
.code web.go
* webserver
.code counter.go
* switch
switch coinflip() {
case "heads":
heads++
case "tails":
tails++
default:
fmt.Println("landed on edge!")
}
_tagless_ switch.
func Signum(x int) int {
switch {
case x > 0:
return +1
default:
return 0
case x < 0:
return -1
}
}
* Other
Struct
type Point struct {
X, Y int
}
var p Point
Pointers
var s string
p := &s
s2 = *p
var p Point
p.X = 1
var pp *Point
pp.X = 1
* The Go Programming Language
.image book.jpg
Всего 400 страниц.
* Документация
.link https://golang.org/doc/effective_go.html Effective Go
.link https://golang.org/pkg/ Документация стандартной библиотеки
.link https://golang.org/doc/faq Go FAQ
.link https://github.com/golang/go/wiki/CodeReviewComments Code Review Comments

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package main
import (
"fmt"
"io/ioutil"
"net/http"
"os"
)
func main() {
for _, url := range os.Args[1:] {
resp, err := http.Get(url)
if err != nil {
fmt.Fprintf(os.Stderr, "fetch: %v\n", err)
os.Exit(1)
}
b, err := ioutil.ReadAll(resp.Body)
resp.Body.Close()
if err != nil {
fmt.Fprintf(os.Stderr, "fetch: reading %s: %v\n", url, err)
os.Exit(1)
}
fmt.Printf("%s", b)
}
}

17
lectures/00-intro/web.go Normal file
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package main
import (
"fmt"
"log"
"net/http"
)
func main() {
http.HandleFunc("/", handler) // each request calls handler
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
// handler echoes the Path component of the request URL r.
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "URL.Path = %q\n", r.URL.Path)
}