From: cruiserdan <dan@...>
Date: 2007-12-19T04:31:01+09:00
Subject: Re: Database-like Algorithmic Problem

Interesting problem. Aside from seeing a doctor, my suggestions are in
the comments in the revised variant below:

---

require 'set'

# encapsulate
class DB

  # use hash's default syntax
  def initialize
    @c = Hash.new{ | hash, key | hash[key] = Set.new }
  end

  # was: add, use << to follow ruby idiom for array, set
  # store val with hash for quicker comparison
  def <<(hash)
    hash.each do |key,val|
      @c[key] << [ val, hash ]
    end
  end

  # need a delete operation ...
  def delete(hash)
    @c.delete(hash)
  end

  # was: match_all, use select to follow ruby enumerable idiom
  # determine candidates on the fly, avoid intersection code using Set
  def select(template)
    good = Set.new; bad = Set.new
    template.each do |key,val1|
      (@c[key]).each do |val2,hash|
        ( val1 === val2 ? good : bad ) << hash unless bad.include?
hash
      end
    end
    return good.to_a
  end

  # was: match_first, use select to follow ruby enumerable idiom
  # determine candidates on the fly, avoid intersection code using Set
  def find(template)
    good = Set.new; bad = Set.new
    template.each do |key,val1|
      (@c[key]).each do |val2,hash|
        ( val1 === val2 ? good : bad ) << hash unless bad.include?
hash
      end
      return good.to_a.first unless good.empty?
    end
    return nil
  end
end


---

HTH!

Dan Yoder
http://dev.zeraweb.com/

On Dec 18, 9:45 am, Christophe Mckeon <chromatoph...@gmail.com> wrote:
> > You are crazy.  Please contact a doctor ASAP. Oh, sorry. :-)
>
> :)
>
>
>
> > I think you are on a pretty good way.  Here's what I would do
> > differently:
>
> > ...
>
> thanks robert. yeah i'd like to do some caching, but as hashes are
> constantly
> added and removed from the collection, i'll have to weigh up the
> overhead of managing a cache, maybe even implement it and do some
> profiling w/ and w/o. guess i'll have to read up on cache algs.
>
> regards,
> _c
>
> --
> Posted viahttp://www.ruby-forum.com/.