gistfile1.lua

require 'luarocks.require'
require 'rex'
require 'socket'

-- returns tag, id and classes
function parse_haml_tag_using_regex(str)
  return rex.match(str, '(%[a-z0-9]*)?(#[a-z0-9-_]*)?(\.[a-z0-9-_\.]*)?')
end

-- returns tag, id and classes
function parse_haml_tag_using_patterns(str)
  return string.match(str, '(%%[%w]*)'), 
    string.match(str, '(#[%w-_]*)'),
    string.match(str, '(%.[%w-_%.]*)')
end

function benchmark(str, repetitions, func)
  local start_time = socket.gettime() * 1000
  for i = 0, repetitions do
    func(str)
  end
  return socket.gettime() * 1000 - start_time
end

local str = "%h2#my_id.class1.class2.class3"
print("Patterns: " .. benchmark(str, 10000, parse_haml_tag_using_patterns) .. " milliseconds")
print("Regex: " .. benchmark(str, 10000, parse_haml_tag_using_regex) .. " milliseconds")

-- on my machine:
-- Patterns: 32.72509765625 milliseconds
-- Regex: 63.48095703125 milliseconds