Verifying data type

Hello guys,

I have a function like this


CREATE OR REPLACE FUNCTION "public"."f_tipo_campo" (varchar) RETURNS 
numeric AS
'declare p_valor ALIAS FOR $1; v_resultado varchar;
begin  v_resultado := 1;
<>   return v_resultado;
<>end;
<><>' LANGUAGE 'plpgsql'

<>

<>
I need to verify if the data in p_valor is just number or it is a string.
What is the best way to do this?

Here is the original function in Oracle PL/SQL

create or replace function f_tipo_campo (p_valor varchar) return number is
  v_resultado number;
  v_number    number;

begin
  begin
     select p_valor
       into v_number from dual;
     v_resultado := 0;
  exception
     when others then
        v_resultado := 1;
  end;
  return v_resultado;

end;

/

show err

--
Elieser Leão
Sorry for my bad english...