From: Bulat Ziganshin <bulatz@...>
Date: 2002-09-25T16:51:05+09:00
Subject: constructing closures on the fly

Hello ruby-talk,

  ok, that's my problem: i had large list of filenames (100k strings,
  for example) and need to quickly sort them based on constructed
  criterion. This criterion gived by user in form of string containing
  letters 'ensgi3', where each letter maps to expression, parameterized
  by filename, so:

  filenames.sort_files "en"
  must be equal to
  filenames.sort_by {|name| [ext(name), name(name)]}

  filenames.sort_files "ges"
  must be equal to
  filenames.sort_by {|name| [group(name), ext(name), size(name)]}

  and so on. Currently i use non-functional approach:

  def sort_files(crit)
    sort_by {|name| construct(crit,name)}
  end

  def construct(crit,name)
    arr = []
    crit.each_byte {|c|
      case c
      when ?g then arr << group(name)
      ....
      end
    }
    arr
  end

  while faster approach will be:

  def sort_files(crit)
    sort_by convert_crit(crit)
  end

  
Best regards,
 Bulat                          mailto:bulatz@integ.ru