From: Michel Demazure <michel@...>
Date: 2007-10-31T05:31:11+09:00
Subject: Code to DRY

This is a simplified version of the problem I have. I work with
"ordered" classes, i.e. having a method a.le?(b) (le = lower or equal).
But I want two constants MIN and MAX, same for all classes, with
MIN.le?(a) == true, a.le?(MAX) == true, a.le?(MIN) only if a == MIN and
MAX.le?(a) only if a == MAX. Moreover, I want a default a.le?(b) when
le? is not defined for a.Class.

This is a possibility

class MaxClass
  def le?(other); other == self ; end
end
class MinClass
  def le?(other); true ; end
end
MAX = MaxClass.new
MIN = MinClass.new

def method_missing(name, *args)
  if name == "le?"
    case args[0]
      when MAX : true
      when MIN : false
      else
        # real thing for default
    end
  else
    super
  end
end

class Klass1
  def le?(other)
    case other
      when MAX : true
      when MIN : false
      else
        # real thing for Klass1
    end
  end
end

class Klass2
  def le?(other)
    case other
      when MAX : true
      when MIN : false
      else
        # real thing for Klass1
    end
  end
end

and so on

Obviously not DRY !
Suggestions ?
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