Re: Back with recursion in COBOL again! -- COBOL400-L

Hello Roman,

sorry I checked the mail a bit late.Thanks a lot for takingthe

                pain of giving such an elaborate solution.
                It really worked!

Now I realise ILE version of AS/400 Languages are featurerich enoughto be at par with any other open system languages like c orjava.

                Thanks for the Enlightenment!
Regards,
s.chand

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Here is better example for factorial, more likely to factorial'spseudo(python)code

# factorial
def factorial(n):

 if n == 0:
   result = 1
 else:
   result = n * factorial(n-1)
 return result

I coded it in COBOL as follows

      IDENTIFICATION DIVISION.
      PROGRAM-ID. FACTORIAL RECURSIVE.
      ENVIRONMENT DIVISION.
      CONFIGURATION SECTION.
      SOURCE-COMPUTER. IBM-AS400.
      OBJECT-COMPUTER. IBM-AS400.
      DATA DIVISION.
      WORKING-STORAGE SECTION.
      01 RESULT       PIC 9(20).
      01 CALL-RESULT  PIC 9(20).
      01 N-MINUS-1    PIC 9(4).
      LINKAGE SECTION.
      01 N            PIC 9(4).

      PROCEDURE DIVISION USING BY VALUE N RETURNING RESULT.
          IF N = 0
             COMPUTE RESULT = 1
          ELSE
             COMPUTE N-MINUS-1 = N - 1
             CALL PROCEDURE 'FACTORIAL'
                  USING BY VALUE N-MINUS-1
                  RETURNING INTO CALL-RESULT
             COMPUTE  RESULT = N * CALL-RESULT
          END-IF.
          GOBACK.

note that I'm using calling by value n

the caller program is here

      IDENTIFICATION DIVISION.
      PROGRAM-ID. RECURTEST.
      ENVIRONMENT DIVISION.
      CONFIGURATION SECTION.
      SOURCE-COMPUTER. IBM-AS400.
      OBJECT-COMPUTER. IBM-AS400.
      SPECIAL-NAMES.
      DATA DIVISION.
      WORKING-STORAGE SECTION.
      01 N           PIC 9(4).
      01 RESULT      PIC 9(20).
      LINKAGE SECTION.
      PROCEDURE DIVISION.
          PERFORM VARYING N FROM 0 BY 1 UNTIL N = 21
            CALL PROCEDURE 'FACTORIAL'
                 USING BY VALUE N
                 RETURNING INTO RESULT
            DISPLAY N "! = " RESULT
          END-PERFORM.
      GOBACK.


now compile the FACTORIAL module, e.g.:
CRTCBLMOD MODULE(EBKPGMP/FACTORIAL) SRCFILE(RM/CBLJAVASRC)
SRCMBR(FACTORIAL)
DBGVIEW(*SOURCE)

create service program TMPPROC, e.g.:
CRTSRVPGM SRVPGM(EBKPGMP/TMPPROC) MODULE(EBKPGMP/FACTORIAL)
EXPORT(*ALL)

compile the RECURTEST module, e.g:
CRTCBLMOD MODULE(EBKPGMP/RECURTEST) SRCFILE(RM/CBLJAVASRC)
SRCMBR(RECURTEST)
DBGVIEW(*SOURCE)

and create the program RECURTEST with entry module RECURTEST linking it
with the saervice program TMPPROC, e.g:
CRTPGM PGM(EBKPGMP/RECURTEST)
ENTMOD(EBKPGMP/RECURTEST) BNDSRVPGM(EBKPGMP/TMPPROC)

Finally by calling that program CALL RECURTEST you will obtain these
results:

    0000! = 00000000000000000001
    0001! = 00000000000000000001
    0002! = 00000000000000000002
    0003! = 00000000000000000006
    0004! = 00000000000000000024
    0005! = 00000000000000000120
    0006! = 00000000000000000720
    0007! = 00000000000000005040
    0008! = 00000000000000040320
    0009! = 00000000000000362880
    0010! = 00000000000003628800
    0011! = 00000000000039916800
    0012! = 00000000000479001600
    0013! = 00000000006227020800
    0014! = 00000000087178291200
    0015! = 00000001307674368000
    0016! = 00000020922789888000
    0017! = 00000355687428096000
    0018! = 00006402373705728000
    0019! = 00121645100408832000
    0020! = 02432902008176640000

So, from the above example it follows, that using modules and serviceprograms the recursion in ILE COBOL is possible in the similar manner asin the other languages.

Roman


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