i cannot able to delete the sql function permenently

Hi I am created a function


CREATE FUNCTION one(float,float) RETURNS float AS $$
  select  $1+$2 AS result;
$$ LANGUAGE SQL;
 Its worked

Then
  I droped the function
        Drop function one(float,float)
Its also worked

    Then I typed
   Select one(18.5,12.4)

 Ho=E2=80=A6 the result  appers as 31.9

How is it
???
Pls replay