1. List comprehensions in Python made the edits1 function more elegant IMO.
2. The boolean expression in the correct function evaluates empty sets/arrays as false in Python but not in Ruby, so I had to add the “result.empty? ? nil : result” expression to several functions. I expect there’s a better way to handle this also.

Otherwise, the translation was pretty straightforward.

Here’s a link to Norvig’s page:
http://www.norvig.com/spell-correct.html

That page includes a link to a text file that I saved locally as
holmes.txt: http://www.norvig.com/holmes.txt

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

After you’ve saved the holmes.txt file, load the code into irb and call the correct function with a string as follows:

badkins:~/sync/code/ruby$ irb
irb(main):001:0> require 'spelling_corrector.rb'
=> true
irb(main):002:0> correct "whree"
=> "where"

http://www.justin.tv/hackertv/97554/Startup_School

Peter Norvig, Paul Graham, Marc Andreessen, Mike Arrington, Jeff Bezos, David Heinemeier Hansson, etc.

The most impressive people I know are all terrible procrastinators. So could it be that procrastination isn’t always bad?

Most people who write about procrastination write about how to cure it. But this is, strictly speaking, impossible. There are an infinite number of things you could be doing. No matter what you work on, you’re not working on everything else. So the question is not how to avoid procrastination, but how to procrastinate well.

It’s ironic that I read this essay while procastinating :) To read the rest, click the previous link.

Although I’ve read a fair amount about him, this was the first time I heard his voice. I noticed he sounds very much like Regis Philbin :)

UPDATE:
Here are a few more BBC video links:

Google Video Link