def coerce(other)
      if other.is_a? InternalComplex
        return other, self
      elsif other.is_a? Complex
        return InternalComplex.new( other.real, other.imag ), self
      else
        return InternalComplex.new( other, 0 ), self
      end
    end
def coerce(other)
      if other.is_a? InternalComplex
        return other, self
      elsif other.is_a? Complex
        return InternalComplex.new( other.real, other.imag ), self
      else
        return InternalComplex.new( other, 0 ), self
      end
    end
Coerce with other object

 @param [InternalComplex,Object] other Other object.

 @return [Array<InternalComplex>] Result of coercion.

 @private