一，单词替换

1 package main  2   3 import (  4     "bufio"  5     "fmt"  6     "io"  7     "io/ioutil"  8     "log"  9     "os" 10     "path/filepath" 11     "regexp" 12     "strings" 13 ) 14  15 var britishAmerican = "british-american.txt" 16  17 func init() { 18     dir, _ := filepath.Split(os.Args[0]) 19     britishAmerican = filepath.Join(dir, britishAmerican) 20     //fmt.Println("dir %s,file %s",dir,britishAmerican) 21 } 22  23 func main() { 24     inFilename, outFilename, err := filenamesFromCommandLine() 25     if err != nil { 26         fmt.Println(err) 27         os.Exit(1) 28     } 29     inFile, outFile := os.Stdin, os.Stdout 30     if inFilename != "" { 31         if inFile, err = os.Open(inFilename); err != nil { 32             log.Fatal(err) 33         } 34         defer inFile.Close() 35     } 36     if outFilename != "" { 37         if outFile, err = os.Create(outFilename); err != nil { 38             log.Fatal(err) 39         } 40         defer outFile.Close() 41     } 42  43     if err = americanise(inFile, outFile); err != nil { 44         log.Fatal(err) 45     } 46 } 47  48 func filenamesFromCommandLine() (inFilename, outFilename string, err error) { 49     if len(os.Args) > 1 && (os.Args[1] == "-h" || os.Args[1] == "--help") { 50         err = fmt.Errorf("usage :%s [<] infile.txt [>] outfile.txt", 51             filepath.Base(os.Args[0])) 52         return "", "", err 53     } 54     if len(os.Args) > 1 { 55         inFilename = os.Args[1] 56         if len(os.Args) > 2 { 57             outFilename = os.Args[2] 58         } 59     } 60     if inFilename != "" && inFilename == outFilename { 61         log.Fatal("won't overwrite the infile") 62     } 63     return inFilename, outFilename, nil 64 } 65  66 func americanise(inFile io.Reader, outFile io.Writer) (err error) { 67     reader := bufio.NewReader(inFile) 68     writer := bufio.NewWriter(outFile) 69     defer func() { 70         if err == nil { 71             err = writer.Flush() 72         } 73     }() 74  75     var replacer func(string) string 76     if replacer, err = makeReplacerFunction(britishAmerican); err != nil { 77         return err 78     } 79     wordRx := regexp.MustCompile("[A-Za-z]+") 80     eof := false 81     for !eof { 82         var line string 83         line, err = reader.ReadString('\n') 84         if err == io.EOF { 85             err = nil 86             eof = true 87         } else if err != nil { 88             return err 89         } 90         line = wordRx.ReplaceAllStringFunc(line, replacer) 91         if _, err = writer.WriteString(line); err != nil { 92  93             return err 94         } 95     } 96     return nil 97 } 98  99 func makeReplacerFunction(file string) (func(string) string, error) {100     rawBytes, err := ioutil.ReadFile(file)101     if err != nil {102         return nil, err103     }104     text := string(rawBytes)105     usForBritish := make(map[string]string)106     lines := strings.Split(text, "\n")107     for _, line := range lines {108         fields := strings.Fields(line)109         if len(fields) == 2 {110             usForBritish[fields[0]] = fields[1]111         }112     }113 114     return func(word string) string {115         if usWord, found := usForBritish[word]; found {116             return usWord117         }118         return word119     }, nil120 }

 

这次的格式终于没错

这个功能里面，我觉得有几个要点，一个是闭包，一个是正则的替换，还有个defer做后事～

简单理解一下闭包，在构造一个函数的时候，同时让这个函数自带了一些数据等其他内容，比如这里定义这个replacer函数的时候，首先定义replacer的私有数据map，然后返回了使用这个map的函数。这样在调用replacer的时候，就可以使用这个map点数据。（好像说的有点混乱。。）

正则和defer就没啥好说的了。。