# File lib/math_ml/element.rb, line 187
                def set_align_attribute(name, a, default)
                        if a.is_a?(Array) && a.size>0
                                value = ""
                                a.each do |i|
                                        value << " "+i
                                end
                                if value =~ /^( #{default})*$/
                                        @attributes.delete(name)
                                else
                                        @attributes[name] = value.strip
                                end
                        else
                                @attributes.delete(name)
                        end
                end