remove ties from lilypond

remove_ties.rb

# Useful for adapting editions of early music to create versions without barlines
# Ties must not cross lines
# Before running this, use the "explicit durations" transformation in Frescobaldi

TIE_RE = %r(([a-g][fs]?)([,']?)(\d)\s*~\s*\|\s*\1(\d))

ARGF.readlines.each do |line|
#  STDERR.puts "Original line: #{line}"
  while(line.match?(TIE_RE))
    line.match(TIE_RE) do |m|
      (pitch, octave, dur1, dur2) = m.captures
      if(dur1 == "1" && dur2 == "1")
        newdur = '\breve'
      elsif(dur1 == dur2)
        newdur = (dur1.to_i / 2).to_s
      elsif dur1.to_i == (dur2.to_i / 2)
        newdur = "#{dur1}."
      elsif dur2.to_i == (dur1.to_i / 2)
        newdur = "#{dur2}."
      else
        STDERR.puts("??? weird tie '#{s}'")
        next
      end
      newstuff = "#{pitch}#{octave}#{newdur}"
      STDERR.puts("Replaced #{m} with #{newstuff}")
      line = "#{m.pre_match}#{pitch}#{octave}#{newdur}#{m.post_match}"
    end
  end

  if line.match?(/~/)
    STDERR.puts("line #{line} still has ties??")
  end

  puts line
end