def lookup( value, stride )
      if value.is_a? Variable
        Lookup.new self, value, stride
      else
        self.class.new @value + ( stride.get *
                                  self.class.target.storage_size ) * value.get
      end
    end
def lookup( value, stride )
      if value.is_a? Variable
        Lookup.new self, value, stride
      else
        self.class.new @value + ( stride.get *
                                  self.class.target.storage_size ) * value.get
      end
    end
Lookup element of an array

 @param [Node] value Index of element.
 @param [Node] stride Stride for iterating over elements.

 @private