Re: Leave outside of DO group???

Sometimes this principle causes unnecessary nesting or duplication of code. Say you are reading a file. Do you have two read statements, or do you introduce an extra level of nesting in the loop to avoid processing after no record found?

read
do while not eof
process
read
end do

or

do until eof
read
if not eof
process
end if
end do

or short cut it

do while true
read
if eof then leave
process
end do

The best practices being violated are (respectively):
* do not repeat yourself
* minimize nesting
* only one in and only one out

So which would you choose? It really comes down to shop standard, and any of these are easy enough to understand, but personally I find that excessive nesting is the biggest culprit in making code unreadable.


Mark Murphy
STAR BASE Consulting, Inc.
mmurphy@xxxxxxxxxxxxxxx


-----John McKee <jmmckee@xxxxxxxxxxxxxx> wrote: -----
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
From: John McKee <jmmckee@xxxxxxxxxxxxxx>
Date: 07/23/2013 07:18PM
Subject: Re: Leave outside of DO group???

I'm confused. I had a teacher, years ago, who was adamant - one way
in and one way out. How is LEAVE considered structured? Violates the
teacher's rule, since there are now multiple ways that a loop could be
exited. His preferred method was to test at the top.

I don't mean to start an argument. Just trying to understand how
multiple exit paths is considered structured.

I have had to debug programs with multiple exit paths. Process was
more involved.

John McKee

On Tue, Jul 23, 2013 at 4:58 PM, Booth Martin <booth@xxxxxxxxxxxx> wrote:

Could he do a NOT/Else with the NOt MonMsg... else leave?

On 7/23/2013 4:51 PM, Dan Kimmel wrote:

Still, I like the concept. It'd be a way to get out of a block of code without a GOTO. The Do .. EndDo marks the block of code. Are there other ways to jump out of a block in CL structured op codes?

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-
bounces@xxxxxxxxxxxx] On Behalf Of CRPence
Sent: Tuesday, July 23, 2013 4:13 PM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: Leave outside of DO group???

On 23 Jul 2013 13:48, DrFranken wrote:

I wrote this snippet of code:

Do
ChkObj QSTRUPEX1 *Pgm /* Check for exit program. */
MonMsg CPF9800 EXEC(Leave) /* Not there or Not Authorized */
Call QSTRUPEX1 /* Run it. */
MonMsg CPF0000
EndDo


At the LEAVE Statement I get this error:
* CPD0883 30 LEAVE command found outside of DO group.

But it sure appears to be inside a Do group to me!

Am I in error if I 'complain' to the fine folks in the land of IBM
i?

AFaIK the error is correct, and ...

The implied command label [CMDLBL(*CURRENT)] is, as worded in the
message CPD089A, is not "associated with an active DOWHILE, DOUNTIL, or
DOFOR group". The additional\second-level text of that CPD0883 [e.g. as
presented by F1=Help] should further state that "The LEAVE command must
be inside a DOWHILE, DOUNTIL, or DOFOR command group."

FWiW: Coding the MONMSG CPF0000 as shown is not a good practice; just
as well remove the prior CHKOBJ and MONMSG to get effectively the same
results with less work.

--
Regards, Chuck
--

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