Contents

class Predicate
  module In
    include Expr

    def priority
      80
    end

    def left
      self[1]
    end
    alias :identifier :left

    def right
      self[2]
    end

    def &(other)
      # we only optimize with another In
      return super unless other.is_a?(In)

      # we only optimize is same free variables
      fv = free_variables
      return super unless fv.size == 1 && fv == other.free_variables

      # we only optimize if both right terms are literals
      return super unless right.literal? and other.right.literal?

      intersection = right.value & other.right.value
      if intersection.empty?
        Factory.contradiction
      elsif intersection.size == 1
        Factory.eq(fv.first, [:literal, intersection.first])
      else
        Factory.in(fv.first, intersection)
      end
    end

    def free_variables
      @free_variables ||= identifier.free_variables
    end

    def constant_variables
      if right.literal? and right.value.size == 1
        free_variables
      else
        []
      end
    end

    def constants
      if right.literal? and right.value.size == 1
        { identifier.name => right.value.first }
      else
        {}
      end
    end

    def dyadic_priority
      800
    end

    def evaluate(tuple)
      values = right.evaluate(tuple)
      values.include?(identifier.evaluate(tuple))
    end

  end
end

Version data entries

2 entries across 2 versions & 1 rubygems

Version	Path
predicate-2.2.0	lib/predicate/nodes/in.rb
predicate-2.1.0	lib/predicate/nodes/in.rb