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require "digest/md5" | |
class SpellChecker | |
# num_bits is how many bits the hash function should produce. | |
def initialize(dictionary_name, num_bits) | |
@num_bits = num_bits | |
@bitmap = [] | |
load_dictionary(dictionary_name) | |
end | |
# Returns true if the word is a real word. False otherwise. | |
def check(word) | |
bloom_filter(word).inject(true) { |is_real, i| is_real && @bitmap[i] } | |
end | |
private | |
# Takes a word and generates an array of indices. | |
def bloom_filter(word) | |
# Generate the digest then translate it to binary. | |
binary = Digest::MD5.hexdigest(word).to_i(16).to_s(2) | |
# Grab arbitrary sections to generate a number. | |
[10, 43, 81].map do |i| | |
binary.slice(i, @num_bits).to_i(2) | |
end | |
end | |
# Loads the given dictionary and uses the bloom filter to fill out the | |
# bitmap. | |
def load_dictionary(filename) | |
File.open(filename, "r").each_line do |line| | |
bloom_filter(line.strip).each do |i| | |
@bitmap[i] = true | |
end | |
end | |
end | |
end | |
checker = SpellChecker.new("/usr/share/dict/words", 20) | |
while true | |
print "Type in a word (q to quit): " | |
word = gets.strip | |
break if word == "q" | |
print ">>> #{word} is #{checker.check(word) ? "" : "NOT "}a word\n" | |
end |
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