From: Enrique Meza <emeza@...>
Date: 2004-02-05T11:15:03+09:00
Subject: Re: eistein's riddle

Very interesting code... but  hangup forever...

./einstein.rb:24:in `find': Interrupt   from ./einstein.rb:24:in
`detect'
        from ./einstein.rb:24:in `each'
        from ./einstein.rb:24:in `detect'
        from ./einstein.rb:24:in `find'
        from ./einstein.rb:28:in `nationality'
        from ./einstein.rb:40

If i runnit with irb:


einstein.rb(main):061:0> puts "The " + pet("fish").nationality + " owns
the fish"
The Brit owns the fish
=> nil

But seems wrong answer...

 I think  in 'detect' line is the bug...


----------- CODE ---------------------------------------

#!/usr/local/bin/ruby

class Amb
    def initialize
        @failureContinuation = proc{raise "Amb goal tree exhausted"}
    end
     
    def fail
        @failureContinuation.call(nil)
    end
     
    def assert(bool)
        fail unless bool
    end
     
    def choose(procArray)
        kPrev = @failureContinuation
        callcc do |kEntry|
            procArray.each do |p|
                callcc do |kNext|
                    @failureContinuation = proc do |v|
                        @failureContinuation = kPrev
                        kNext.call(v)
                    end
                    kEntry.call(p.call)
                end
            end
            kPrev.call(nil)
        end
    end
                                                                                
    def one_of(enumerable)
        choose(enumerable.collect{|ea| proc{ea}})
    end
                                                                                
    def maybe
        one_of([true, false])
    end
end

$colors = ["red", "white", "yellow", "blue", "green"]
$nationalities = ["Brit", "Swede", "Dane", "Norwegian", "German"]
$beverages = ["tea", "coffee", "milk", "beer", "water"]
$cigars = ["Pall Mall", "Blends", "Dunhill", "Prince", "Bluemasters"]
$pets = ["dogs", "birds", "cats", "horse", "fish"]
 
class House
  attr_reader :color, :nationality, :beverage, :cigar, :pet
 
  def initialize
    @color = $amb.one_of($colors)
    @nationality = $amb.one_of($nationalities)
    @beverage = $amb.one_of($beverages)
    @cigar = $amb.one_of($cigars)
    @pet = $amb.one_of($pets)
  end
end
 
def find(property, value)
  $houses.detect{|h| h.send(property) == value} || $amb.fail
end
 
def color(s) find(:color, s) end
def nationality(s) find(:nationality, s) end
def beverage(s) find(:beverage, s) end
def cigar(s) find(:cigar, s) end
def pet(s) find(:pet, s) end
 
def next_door(h1, h2)
  ($houses.index(h1) - $houses.index(h2)).abs == 1
end
 
$amb = Amb.new
$houses = (1..5).collect{House.new}
puts "Finding.... red..\n"
$amb.assert(nationality("Brit").color == "red")
#fact 2
puts "Finding.... dogs..\n"
$amb.assert(nationality("Swede").pet == "dogs")
#fact 3
$amb.assert(nationality("Dane").beverage == "tea")
#fact 4
$amb.assert(houses.index(color("white")) -
houses.index(color("green")) == 1)
#fact 5
$amb.assert(color("green").beverage == "coffee")
#fact 6
$amb.assert(cigar("Pall Mall").pet == "birds")
#fact 7
$amb.assert(color("yellow").cigar == "Dunhill")
#fact 8
$amb.assert(houses[2].beverage == "milk")
#fact 9
$amb.assert(houses[0].nationality == "Norwegian")
#fact 10
$amb.assert(next_door(cigar("Blends"), pet("cats")))
#fact 11
$amb.assert(next_door(cigar("Dunhill"), pet("horse")))
#fact 12
$amb.assert(cigar("Bluemasters").beverage == "beer")
#fact 13
$amb.assert(nationality("German").cigar == "Prince")
#fact 14
$amb.assert(next_door(nationality("Norwegian"), color("blue")))
#fact 15
$amb.assert(next_door(cigar("Blends"), beverage("water")))
puts "All 15 facts...\n"
                                                                                
Regards,
-- 
Enrique Meza <emeza@saisamx.com>