Date:         Tue, 14 Jul 1998 19:38:19 GMT
Reply-To:     Andreas Grueninger <grueni@STUTTGART.NETSURF.DE>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Andreas Grueninger <grueni@STUTTGART.NETSURF.DE>
Organization: LF.net GmbH, Internet Services, Stuttgart, Germany
Subject:      Re: Modular recursion in COBOL and SAS (was: Re:Recursion in
              SAS-the exact query)

Hmm,
 
very nice discussion about english grammar. I appreciate this very
much to improve my knowledge about the english language (I am german).
Back to SAS:
Paul, do you really think this is recursion if you go to the label?
I guess it is something like a restart of the do loops. If it would be
a real recursion the value i should be restored if the recursive
called function (here a link/return or for the COBOL freaks a perform)
is finished. This is not the case. The values of the index i after the
LINK part in the do loop starts with the last value of i before the
last jumping out and is incremented by 1 for each RETURN. This is
somewhat bizzare and IMHO good for nothing.
I changed the code a little bit to show the values of a new variable x
and the index i.
 
BTW:
And for Aston Lexmart (the C and Assembler freak):
Real recursion can be done easily in SAS with SCL and calling of
methods. So it would be easy to implement a quicksort. The more
intelligent solution would be to use proc sort.
 
DATA _NULL_;
     ARRAY A(9) (4,7,3,1,9,6,2,8,5);
     KEY   =  1;
     PIVOT =  9;
     STEP  = -1;
     x = 0;
     IF 0 THEN DO;
         PART:
         DO J=1 TO 9; PUT A(J) @; END; PUT; *SHOW CURRENT STATE OF
ARRAY;
         DO I = PIVOT TO KEY BY STEP;
               IF STEP * (A(I) - A(KEY)) > 0 THEN DO;
                    T=A(I); A(I)=A(KEY); A(KEY)=T; *SWAP ELEMENTS;
                    PIVOT = KEY - STEP;
                    PUT key= @;
                    KEY   = I;
                    STEP  = (-1) * STEP; *SWAP SWEEP DIRECTION;
                    x + 1;
                    PUT i= x= @;
                    LINK PART; *CALL ITSELF;
                    PUT x= i=;
               END;
         END;
         RETURN;
     END;
     LINK PART;
RUN;
4 7 3 1 9 6 2 8 5
KEY=1 I=7 X=1 2 7 3 1 9 6 4 8 5
KEY=7 I=2 X=2 2 4 3 1 9 6 7 8 5
KEY=2 I=4 X=3 2 1 3 4 9 6 7 8 5
X=3 I=5
X=3 I=6
X=3 I=7
 
 
---------------------------
Andreas Grueninger
 
PRIVAT: grueni@stuttgart.netsurf.de
OFFICIAL: grueninger@lfl.bwl.de
---------------------------