[Casimiro Notevi]

primero ejecuta esto:

DECLARE EXTERNAL FUNCTION abs 
    DOUBLE PRECISION
    RETURNS DOUBLE PRECISION BY VALUE
    ENTRY_POINT 'IB_UDF_abs' MODULE_NAME 'ib_udf';

y luego esto:

CREATE PROCEDURE AAAAAAAAA (
    chaar char(10))
returns (
    num integer)
as
begin
num=abs(chaar);
  /* Procedure Text */
  suspend;
end