A Tour of Go

Exercise: 43

package main

import (
    "code.google.com/p/go-tour/wc"
    "strings"
)

func WordCount(s string) map[string]int {
    words  := strings.Fields(s)
    wordmap := make(map[string]int)
    for i :=0; i < len(words); i++ {
        word := words[i]
        if val,ok := wordmap[word]; ok {
            wordmap[word] = val+1
        } else {
         	wordmap[word] = 1
        }
    }
    return wordmap
}

func main() {
    wc.Test(WordCount)
}

Exercise: 69

package main

import (
	"fmt"
	"sync"
)

type Fetcher interface {
	// Fetch returns the body of URL and
	// a slice of URLs found on that page.
	Fetch(url string) (body string, urls []string, err error)
}

var (
	seen = map[string]bool{}
	wg   sync.WaitGroup
)

// Crawl uses fetcher to recursively crawl
// pages starting with url, to a maximum of depth.
func Crawl(url string, depth int, fetcher Fetcher) {
	// TODO: Fetch URLs in parallel.
	// TODO: Don't fetch the same URL twice.
	// This implementation doesn't do either:

	defer wg.Done()
	if depth <= 0 || seen[url] {
		return
	}
	seen[url] = true
	body, urls, err := fetcher.Fetch(url)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Printf("found: %s %q\n", url, body)
	wg.Add(len(urls))
	for _, u := range urls {
		go Crawl(u, depth-1, fetcher)
	}

	return
}

func main() {
	wg.Add(1)
	Crawl("http://golang.org/", 4, fetcher)
	wg.Wait()
}

// fakeFetcher is Fetcher that returns canned results.
type fakeFetcher map[string]*fakeResult

type fakeResult struct {
	body string
	urls []string
}

func (f fakeFetcher) Fetch(url string) (string, []string, error) {
	if res, ok := f[url]; ok {
		return res.body, res.urls, nil
	}
	return "", nil, fmt.Errorf("not found: %s", url)
}

// fetcher is a populated fakeFetcher.
var fetcher = fakeFetcher{
	"http://golang.org/": &fakeResult{
		"The Go Programming Language",
		[]string{
			"http://golang.org/pkg/",
			"http://golang.org/cmd/",
		},
	},
	"http://golang.org/pkg/": &fakeResult{
		"Packages",
		[]string{
			"http://golang.org/",
			"http://golang.org/cmd/",
			"http://golang.org/pkg/fmt/",
			"http://golang.org/pkg/os/",
		},
	},
	"http://golang.org/pkg/fmt/": &fakeResult{
		"Package fmt",
		[]string{
			"http://golang.org/",
			"http://golang.org/pkg/",
		},
	},
	"http://golang.org/pkg/os/": &fakeResult{
		"Package os",
		[]string{
			"http://golang.org/",
			"http://golang.org/pkg/",
		},
	},
}