Simple script to generate combinations of the elements from the periodic table to create strings provided by the user. Very inefficient, and probably buggy, but it works well enough to play with my http://www.thinkgeek.com/interests/giftsunder10/8fc5/ :)

periodic-phrase

#!/usr/bin/env ruby

abort "You need to provide a string as the last argument" if ARGV.empty?

$debug = true if (ARGV & %w(-d -v --debug --verbose)).any?

def ruler_for(used)
  size = used.map(&:size).inject(:+) + used.size - 1
  "-" * size
end

def debug(msg)
  $stderr.puts msg if $debug
end

ELEMENTS = %W( Ac Ag Al Am Ar As At Au B Ba Be Bh Bi Bk Br C Ca Cd Ce Cf Cl Cm
  Co Cr Cs Cu Db Dy Er Es Eu F Fe Fm Fr Ga Gd Ge H He Hf Hg Ho Hs I In Ir K Kr
  La Li Lr Lu Md Mg Mn Mo Mt N Na Nb Nd Ne Ni No Np O Os P Pa Pb Pd Pm Po Pr Pt
  Pu Ra Rb Re Rf Rh Rn Ru S Sb Sc Se Sg Si Sm Sn Sr Ta Tb Tc Te Th Ti Tl Tm U V
  W Xe Y Yb Zn Zr )

input = ARGV.last.downcase.gsub(/[^a-z]/, '')
used, skip, tried_combinations = [], [], []

while input.length.nonzero?

  element = (ELEMENTS - used - skip).detect {|el| input =~ /^#{el}/i }
  debug "-- Attempting with #{element}" if element

  if element.nil?
    debug "-- skip: #{skip.inspect}"
    debug "-- used: #{used.inspect}"

    if used.empty? || tried_combinations.include?(used)
      abort "can't write that phrase, sorry :("
    end

    tried_combinations << used
    last = used.pop
    skip << last

    input = last.downcase + input
  else
    used << element
    skip.clear

    input = input.gsub(/^#{element}/i, "")
  end
end

puts ruler_for(used)
puts used.join(" ")
puts ruler_for(used)

puts "  Using: #{used.join(", ")}"