Just for fun, I rewrote Peter Norvig’s well-known spelling corrector in the Go programming language. The up-to-date code is at here. A snapshot of it is:
package main
import (
"io/ioutil"
"regexp"
"fmt"
"strings"
)
func train(training_data string) map[string]int {
NWORDS := make(map[string]int)
pattern := regexp.MustCompile("[a-z]+")
if content, err := ioutil.ReadFile(training_data); err == nil {
for _, w := range pattern.FindAllString(strings.ToLower(string(content)), -1) {
NWORDS[w]++;
}
} else {
panic("Failed loading training data. Get it from http://norvig.com/big.txt.")
}
return NWORDS
}
func edits1(word string, ch chan string) {
const alphabet = "abcdefghijklmnopqrstuvwxyz"
type Pair struct{a, b string}
var splits []Pair
for i := 0; i < len(word) + 1; i++ {
splits = append(splits, Pair{word[:i], word[i:]}) }
for _, s := range splits { // deletes
if len(s.b) > 0 { ch <- s.a + s.b[1:] }}
for _, s := range splits { // transposes
if len(s.b) > 1 { ch <- s.a + string(s.b[1]) + string(s.b[0]) + s.b[2:] }}
for _, s := range splits { // replaces
for _, c := range alphabet { if len(s.b) > 0 { ch <- s.a + string(c) + s.b[1:] }}}
for _, s := range splits { // inserts
for _, c := range alphabet { ch <- s.a + string(c) + s.b }}
}
func edits2(word string, ch chan string) {
edits1ch := make(chan string, 10)
go func() {
edits1(word, edits1ch)
ch <- ""}()
for e1 := range edits1ch {
if e1 == "" { break }
edits1(e1, ch)
}
}
func correct(word string, NWORDS map[string]int) string {
ch := make(chan string)
go func() {
ch <- word
edits1(word, ch)
edits2(word, ch)
ch <- ""
}()
maxFreq := 0
correction := ""
for word := range ch {
if word == "" { return correction }
if freq, present := NWORDS[word]; present && freq > maxFreq {
maxFreq, correction = freq, word
}
}
return ""
}
func main() {
model := train("big.txt")
fmt.Println(correct("speling", model))
fmt.Println(correct("korrecter", model))
}
I used 57 non-empty lines of source code to express this algorithm in Go. For numbers of lines with other programming languages, please scroll down to the end of the original post.
Posted by cxwangyi 
