如题 新手。。因为要做作业接触go语言

func Map(value string) *list.List {
}

就是要返回一个list 那应该怎么样创建list和把值写入list呢？

。。

package main
import (
"container/list"
"fmt"
"strings"
)
func main() {
items := list.New()
for _, x := range strings.Split("ABCDEFGH", "") {
items.PushFront(x)
}
items.PushBack(9)
for element := items.Front(); element != nil; element = element.Next() {
switch value := element.Value.(type) {
case string:
fmt.Printf("%s ", value)
case int:
fmt.Printf("%d ", value)
}
}
fmt.Println()
}

for r := 0; r < nreduce; r++ {
file, err = os.Create(ReduceName(fileName, JobNumber, r))
if err != nil {
log.Fatal("DoMap: create ", err);
}
enc := json.NewEncoder(file)
for e := res.Front(); e != nil; e = e.Next() {
kv := e.Value.(KeyValue)
if hash(kv.Key) % uint32(nreduce) == uint32(r) {
err := enc.Encode(&kv);
if err != nil {
log.Fatal("DoMap: marshall ", err);
}
}
}

func DoMap(JobNumber int, fileName string,
nreduce int, Map func(string) *list.List) {
name := MapName(fileName, JobNumber)
file, err := os.Open(name)
if err != nil {
log.Fatal("DoMap: ", err);
}
fi, err := file.Stat();
if err != nil {
log.Fatal("DoMap: ", err);
}
size := fi.Size()
fmt.Printf("DoMap: read split %s %d\n", name, size)
b := make([]byte, size);
_, err = file.Read(b);
if err != nil {
log.Fatal("DoMap: ", err);
}
file.Close()
res := Map(string(b))
// XXX a bit inefficient. could open r files and run over list once
for r := 0; r < nreduce; r++ {
file, err = os.Create(ReduceName(fileName, JobNumber, r))
if err != nil {
log.Fatal("DoMap: create ", err);
}
enc := json.NewEncoder(file)
for e := res.Front(); e != nil; e = e.Next() {
kv := e.Value.(KeyValue)
if hash(kv.Key) % uint32(nreduce) == uint32(r) {
err := enc.Encode(&kv);
if err != nil {
log.Fatal("DoMap: marshall ", err);
}
}
}
file.Close()
}
}

func RunSingle(nMap int, nReduce int, file string,
Map func(string) *list.List,
Reduce func(string,*list.List) string) {
mr := InitMapReduce(nMap, nReduce, file, "")
mr.Split(mr.file)
for i := 0; i < nMap; i++ {
DoMap(i, mr.file, mr.nReduce, Map)
}
for i := 0; i < mr.nReduce; i++ {
DoReduce(i, mr.file, mr.nMap, Reduce)
}
mr.Merge()
}

那个hash是kv.Key在list里的序号吗？
hash是用来计算哈希值的函数。
还有json这个语句不太明白 还有底下的err是用来停止写文件？
不知道你说的是哪里。

func DoReduce(job int, fileName string, nmap int,
Reduce func(string,*list.List) string) {
kvs := make(map[string]*list.List)
for i := 0; i < nmap; i++ {
name := ReduceName(fileName, i, job)
fmt.Printf("DoReduce: read %s\n", name)
file, err := os.Open(name)
if err != nil {
log.Fatal("DoReduce: ", err);
}
dec := json.NewDecoder(file)
for {
var kv KeyValue
err = dec.Decode(&kv);
if err != nil {
break;
}
_, ok := kvs[kv.Key]
if !ok {
kvs[kv.Key] = list.New()
}
kvs[kv.Key].PushBack(kv.Value)
}
file.Close()
}
var keys []string
for k := range kvs {
keys = append(keys, k)
}
sort.Strings(keys)
p := MergeName(fileName, job)
file, err := os.Create(p)
if err != nil {
log.Fatal("DoReduce: create ", err);
}
enc := json.NewEncoder(file)
for _, k := range keys {
res := Reduce(k, kvs[k])
enc.Encode(KeyValue{k, res})
}
file.Close()
}