Spell Correct by Peter Norvig

gistfile1.rb

# Didn't realize this but Brian Adkins wrote a ruby version as well, code is almost identical to my own.

def words text
  text.downcase.scan(/[a-z]+/)
end

def train features
  model = Hash.new(1)
  features.each {|f| model[f] += 1 }
  return model
end

NWORDS = train(words(File.new('holmes.txt').read))
LETTERS = ("a".."z").to_a.join

def edits1 word
  n = word.length
  deletion = (0...n).collect {|i| word[0...i]+word[i+1..-1] }
  transposition = (0...n-1).collect {|i| word[0...i]+word[i+1,1]+word[i,1]+word[i+2..-1] }
  alteration = []
  n.times {|i| LETTERS.each_byte {|l| alteration << word[0...i]+l.chr+word[i+1..-1] } }
  insertion = []
  (n+1).times {|i| LETTERS.each_byte {|l| insertion << word[0...i]+l.chr+word[i..-1] } }
  result = deletion + transposition + alteration + insertion
  result.empty? ? nil : result
end

def known_edits2 word
  result = []
  edits1(word).each {|e1| edits1(e1).each {|e2| result << e2 if NWORDS.has_key?(e2) }}
  result.empty? ? nil : result
end

def known words
  result = words.find_all {|w| NWORDS.has_key?(w) }
  result.empty? ? nil : result
end

def correct word
  (known([word]) or known(edits1(word)) or known_edits2(word) or
    [word]).max {|a,b| NWORDS[a] <=> NWORDS[b] }
end

spell_correct.py

# Jordan Baker's Python Presentation: http://www.slideshare.net/hexsprite/a-taste-of-python-devdays-toronto-2009

# 23 lines of Python code by Peter Norvig http://norvig.com/spell-correct.html

import re, collections

def words(text): 
    return re.findall('[a-z]+', text.lower()) 

def train(features):
    model = collections.defaultdict(lambda: 1)
    for f in features:
        model[f] += 1
    return model

NWORDS = train(words(file('big.txt').read()))

alphabet = 'abcdefghijklmnopqrstuvwxyz'

def edits1(word):
   s = [(word[:i], word[i:]) for i in range(len(word) + 1)]
   deletes    = [a + b[1:] for a, b in s if b]
   transposes = [a + b[1] + b[0] + b[2:] for a, b in s if len(b)>1]
   replaces   = [a + c + b[1:] for a, b in s for c in alphabet if b]
   inserts    = [a + c + b     for a, b in s for c in alphabet]
   return set(deletes + transposes + replaces + inserts)

def known_edits2(word):
    return set(e2 for e1 in edits1(word) for e2 in edits1(e1) if e2 in NWORDS)

def known(words): return set(w for w in words if w in NWORDS)

def correct(word):
    candidates = known([word]) or known(edits1(word)) or known_edits2(word) or [word]
    return max(candidates, key=NWORDS.get)

spell_correct.rb

# 30 lines of Ruby code by Corban Brook (24 lines exluding 'end')

def words(text)
  text.downcase.scan /[a-z]+/
end

def train(words)
  model = Hash.new(0)
  words.each { |w| model[w] += 1 }
  model
end

NWORDS = train(words(File.read('big.txt')))
ALPHABET = *('a'..'z')

def edits1(word)
  s = (0..word.length).collect { |i| [word[0, i], word[i, word.length]] }
  deletes    = s.collect { |a, b| a + b[1, b.length] if b.any? }.compact
  transposes = s.collect { |a, b| a + b[1, 1] + b[0, 1] + b[2, b.length] if b.length > 1 }.compact
  replaces   = s.collect { |a, b| ALPHABET.collect { |c| a + c + b[1, b.length] if b.any? } }.flatten.compact
  inserts    = s.collect { |a, b| ALPHABET.collect { |c| a + c + b } }.flatten
  deletes + transposes + replaces + inserts
end

def known_edits2(word)
  result = []
  edits1(word).each { |e1| result += edits1(e1).select { |e2| NWORDS.has_key? e2 } }
  result.empty? ? nil : result.uniq
end

def known(words)
  result = words.select { |w| NWORDS.has_key? w }
  result.empty? ? nil : result
end

def correct(word)
  (known([word]) or known(edits1(word)) or known_edits2(word) or [word]).max { |a, b| NWORDS[a] <=> NWORDS[b] }
end