gistfile1.rb

require 'active_support/inflector'
require 'benchmark'

# QUICK HACK
class RuleSet
  def initialize
    @rules  = []
    @regexp = nil
  end

  def prepend_rule(pattern, replacement)
    @rules.unshift([pattern, replacement])
    patterns = @rules.each_with_index.map {|rule, i| build_regexp(rule.first, i)}
    @regexp = Regexp.union(*patterns)
  end

  def build_regexp(pattern, i)
    pattern = Regexp.quote(pattern) if pattern.is_a?(String)
    /(?<_#{i}>#{pattern})/
  end

  def apply(word)
    word = word.to_s.dup
    if md = @regexp.match(word)
      name = md.names.detect {|n| md[n]}
      index = name[/\d+/, 0].to_i
      word.gsub!(@rules[index][0], @rules[index][1])
    end
    word
  end
end

rs = RuleSet.new
ActiveSupport::Inflector::Inflections.instance.plurals.each do |pattern, replacement|
  rs.prepend_rule(pattern, replacement)
end

Benchmark.bmbm do |x|
  x.report('AS') { 10000.times { %w(user post person).each {|word| ActiveSupport::Inflector.pluralize(word) }}}
  x.report('RS') { 10000.times { %w(user post person).each {|word| rs.apply(word)}}}
end

__END__
Rehearsal --------------------------------------
AS   5.310000   0.010000   5.320000 (  5.323167)
RS   1.100000   0.000000   1.100000 (  1.096796)
----------------------------- total: 6.420000sec

         user     system      total        real
AS   5.500000   0.010000   5.510000 (  5.545606)
RS   1.150000   0.000000   1.150000 (  1.156264)