To mix incoming data from different sources by avoiding incremental or decremantal
order I tried the following VHDL Code:

ARCHITECTURE
   TYPE gen_folge IS ARRAY (0 TO 7) OF INTEGER;
   CONSTANT reihenfolge : gen_folge := (1,4,2,5,6,3,7,0)  ; -- define order of gen's
   CONSTANT generatoren : INTEGER   := reihenfolge'LENGTH ;
BEGIN
 PROCESS
    VARIABLE ge   : INTEGER ;
 BEGIN
-- starting value:
       ge := reihenfolge'LEFT;
     LOOP ..
        FOR g in 1 TO generatoren LOOP
          ge := reihenfolge'SUCC(ge);          -- get next generator Nummer
-- - - - - - - - - - - - - ^ - - - - - - - - - -
        END LOOP;
     END LOOP;
 END PROCESS

END arch;

----------------------------------------------------------------------------------
SYNOPSYS VHDLAN produces the following error message:

      ge := reihenfolge'SUCC(ge);          -- get next generator Nummer
                       ^
**Error: vhdlan,545 pixwriter_beh_pe.vhd(149):
    Attribute is not defined for this prefix.

Where does this error message result from?
Can I use 'SUCC in this context at all?

English and German answers welcome.

Dieter

ARCHITECTURE arch of a is
   TYPE gen_i IS range 0 TO 7;
   TYPE gen_folge IS ARRAY (gen_i) OF integer;
   CONSTANT reihenfolge : gen_folge := (1,4,2,5,6,3,7,0)  ;
                          -- define order of gen's
   CONSTANT generatoren : integer   := reihenfolge'LENGTH ;
BEGIN
 PROCESS
    VARIABLE ge   : integer ;
    VARIABLE ind  : gen_i ;
 BEGIN
   -- starting value:
   ind := gen_i'LEFT;
   ge := reihenfolge(ind);
   FOR g in 0 TO generatoren-2 LOOP
     ind := gen_i'SUCC(ind);          
     ge := reihenfolge(ind);    
     -- get next generator Number
   END LOOP;
   WAIT;
 END PROCESS;

END arch;

|> Where does this error message result from?

The SUCC attribute applies to expressions of discrete/physical
type/subtype. The expression "reihenfolge" is not of discrete
type (enumeration/interger type) nor of physical type, but a
composite type.

Some expressions that you could apply directly this attribute to
would be "g", "ge", "reihenfolge(g)", "reihenfolge(ge)",... because
they are all of an integer type.

Tchuess,

David Deharbe.