kwic.rb

gistfile1.rb

#!/usr/bin/env ruby

# From "On the Criteria To Be Used in Decomposing Systems into
# Modules", David L. Parnas, in CACM 15.12, p. 1053-1058, 1972:
#
# "The KWIC index system accepts an ordered set of lines, each line is
# an ordered set of words, and each word is an ordered set of
# characters. Any line may be "circularly shifted" by repeatedly
# removing the first word and appending it at the end of the line. The
# KWIC index system outputs a listing of all circular shifts of all
# lines in alphabetical order.
# This is a small system. Except under extreme circumstances (huge
# data base, no supporting software), such a system could be produced
# by a good programmer within a week or two."

lines = Array.new
ARGF.each_line do |line|
  words = line.chomp.split
  words.each_index do |i|
    lines << ( words[i..-1] + words[0...i] ).join(' ')
  end
end
puts lines.sort.uniq

# "When in doubt, use brute force." -- Ken Thompson