Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
139 lines (122 sloc) 2.92 KB
// Package markov handles markov chain generation.
//
// This Markov chain code is taken from the "Generating arbitrary text"
// codewalk: http://golang.org/doc/codewalk/markov/
//
// Minor modifications have been made to make it easier to integrate
// with a webserver and to save/load state
package markov
import (
"encoding/gob"
"fmt"
"math/rand"
"os"
"strings"
"sync"
)
// Prefix is a Markov chain prefix of one or more words.
type Prefix []string
// String returns the Prefix as a string (for use as a map key).
func (p Prefix) String() string {
return strings.Join(p, " ")
}
// Shift removes the first word from the Prefix and appends the given word.
func (p Prefix) Shift(word string) {
copy(p, p[1:])
p[len(p)-1] = word
}
// Chain contains a map ("chain") of prefixes to a list of suffixes.
// A prefix is a string of prefixLen words joined with spaces.
// A suffix is a single word. A prefix can have multiple suffixes.
type Chain struct {
Chain map[string][]string
prefixLen int
mu sync.Mutex
}
// NewChain returns a new Chain with prefixes of prefixLen words.
func NewChain(prefixLen int) *Chain {
return &Chain{
Chain: make(map[string][]string),
prefixLen: prefixLen,
}
}
// Write parses the bytes into prefixes and suffixes that are stored in Chain.
func (c *Chain) Write(in string) (int, error) {
sr := strings.NewReader(in)
p := make(Prefix, c.prefixLen)
for {
var s string
if _, err := fmt.Fscan(sr, &s); err != nil {
break
}
key := p.String()
c.mu.Lock()
c.Chain[key] = append(c.Chain[key], s)
c.mu.Unlock()
p.Shift(s)
}
return len(in), nil
}
// Generate returns a string of at most n words generated from Chain.
func (c *Chain) Generate(n int) string {
c.mu.Lock()
defer c.mu.Unlock()
p := make(Prefix, c.prefixLen)
var words []string
for i := 0; i < n; i++ {
choices := c.Chain[p.String()]
if len(choices) == 0 {
break
}
next := choices[rand.Intn(len(choices))]
words = append(words, next)
p.Shift(next)
}
return strings.Join(words, " ")
}
// Save the chain to a file
func (c *Chain) Save(fileName string) error {
// Open the file for writing
fo, err := os.Create(fileName)
if err != nil {
return err
}
// close fo on exit and check for its returned error
defer func() {
if err := fo.Close(); err != nil {
panic(err)
}
}()
// Create an encoder and dump to it
c.mu.Lock()
defer c.mu.Unlock()
enc := gob.NewEncoder(fo)
err = enc.Encode(c)
if err != nil {
return err
}
return nil
}
// Load the chain from a file
func (c *Chain) Load(fileName string) error {
// Open the file for reading
fi, err := os.Open(fileName)
if err != nil {
return err
}
// close fi on exit and check for its returned error
defer func() {
if err := fi.Close(); err != nil {
panic(err)
}
}()
// Create a decoder and read from it
c.mu.Lock()
defer c.mu.Unlock()
dec := gob.NewDecoder(fi)
err = dec.Decode(c)
if err != nil {
return err
}
return nil
}
You can’t perform that action at this time.