arwagner

;;;;;;;; unify.clj
(ns building-problem-solvers)

(defn unify ... )

;;;;;;; unify_test.clj
(load-file "unify.clj")

(ns building-problem-solvers
    (:use clojure.test))

arwagner

class Foo
  def initialize 
    @x = 3
  end

  def fiddle &block
    instance_eval &block
  end
end

arwagner

instance_eval { 3 }

x = lambda { 3 }
instance_eval &x # wrong number of arguments, 1 for 0

arwagner

fact("x"); query("x"); #=> ["x"]
fact("x"); query("y"); #=> []
fact("is_cool(fred)"); query("is_cool(fred)"); #=> ["is_cool(fred)"]
fact("is_cool(parent_of(fred),on(saturdays))"); query("is_cool(parent_of(fred),on(saturdays))"); #=> ["is_cool(parent_of(fred),on(saturdays))"]

fact("x"); query(":y"); #=> [{":y"=>"x"}]
fact("is_cool(fred)"); query("is_cool(:y)"); #=> [{":y"=>"fred"}]
fact("is_cool(parent_of(fred),on(saturdays))"); query("is_cool(parent_of(fred),:time)"); #=> [{":time"=>"on(saturdays)"}]
fact("is_cool(fred,saturdays)"); query("is_cool(fred)"); #=> []
fact("is_cool(fred,saturdays)"); query("is_cool(fred,:time)"); #=> [{":time"=>"saturdays"}]

arwagner

class Application
  def fact s
  end
end

module RFact
  def fact fact_as_string
    Application.new.fact fact_as_string
  end
end

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class Application
  def fact s
  end
end

module RFact
  def fact fact_as_string
    Application.new.fact fact_as_string
  end
end

arwagner

class Foo
  def not
    3
  end
end

Foo.new.instance_eval { not } #=> syntax error, unexpected '}'
Foo.new.instance_eval { not() } #=> true
Foo.new.send :not #=> 3

arwagner

I found http://groups.google.com/group/growing-object-oriented-software/browse_thread/thread/47695af2c6b5adda fascinating, so I decided to make it a little more concrete. It's also in ruby using rspec, sorry about that. Here's the code under test:

class EligibleForDiscountPolicy
  def initialize transaction, user
    @transaction = transaction
    @user = user
  end

  def decide
    return true if @user.is_gold_member?

arwagner

class ProceduralFiveDigits
  def initialize
    @new_population = Array.new(100) { generate_individual }
    reset
  end

  def evolve
    1000.times do
      100.times do
        @parent_a, @parent_b = [pick_individual, pick_individual]

arwagner

/Users/andrewwagner> which ruby
ruby not found
/Users/andrewwagner> rvm list

rvm rubies

   ruby-1.9.2-p290 [ i386 ]

/Users/andrewwagner> rvm use 1.9.2
Using /Users/andrewwagner/.rvm/gems/ruby-1.9.2-p290