A bit off topic perhaps, but COBOL now supports the following:
EXIT PERFORM (like LEAVE)
EXIT PERFORM CYCLE (like ITERATE)
EXIT PARAGRAPH (like LEAVE but exists the current COBOL paragraph)
EXIT SECTION (like LEAVE but exists the current COBOL section)
You can even exit from a simple block, which you mentioned REXX does not
support:
PERFORM
DISPLAY 'SOMETHING'
IF A = 1
EXIT PERFORM
END-IF
DISPLAY 'SOMETHING ELSE'
END-PERFORM
One thing missing is an "infinite loop" (do forever). I have requested support
of "PERFORM UNTIL EXIT" to allow for this. Feel free to vote for my RFE!
https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=133631
________________________________
From: IBM Mainframe Discussion List <[email protected]> on behalf of Bob
Bridges <[email protected]>
Sent: Tuesday, March 24, 2020 9:19 AM
To: [email protected] <[email protected]>
Subject: GOTOs (was CLIST)
There is such a thing as overdoing GOTOs, but I agree that a blanket
never-do-it rule is counter-productive. I don't often use SIGNAL in REXX,
because I find that its structured features are adequate. But in other
languages I have argued for limited GOTO use.
In COBOL, for example, it seems to me that there's a place for GOTO
TOP-OF-PARAGRAPH (to simulate ITERATE in REXX), GOTO EXIT-PARAGRAPH (to
simulate LEAVE) and GOTO END-OF-PROGRAM (for controlled abend conditions).
These don't violate structured-programming principles, they implement them. In
VBA I freely use Goto IterateSomething (putting the label just before the Next
statement). I don't think PL/1 ever needs it, but I'm glad it's there just in
case.
Even in REXX there's one missing structured ingredient: some way to leave a
~simple~ block. A SELECT comes close, but it's not perfect. Say you're
looping through a list of candidates and have to perform a number of candidates:
do jr=1 to stem.0
v0=stem.jr
if v0='' then iterate
v1=function1(v0)
if v1<5 then iterate
v2=functionv2(v1 + othervalue)
if v2=previous then iterate
say 'TRK:' v0 v1 v2
end
That's great in a controled DO loop. But it's harder in simple block of code.
A SELECT won't do the job, because of the calculations you have to do between
the various tests. I handle it this way:
do 1
if v0='' then leave
v1=function1(v0)
if v1<5 then leave
v2=functionv2(v1+othervalue)
if v2=previous then leave
say 'TRK:' v0 v1 v2
end
I always suspect I'd get complaints from structured enthusiasts if they ever
saw me cheating like that. In VBA I can't "Do 1", but I can do this:
Do 'one time
If v0 = '' Then Exit Do
v1 = function1(v0)
If v1 < 5 Then Exit Do
v2 = functionv2(v1 + othervalue)
If v2 = previous Then Exit Do
MsgBox "TRK: " & v0 & " " & v1 & " " & v2
Loop Until True
---
Bob Bridges, [email protected], cell 336 382-7313
/* Being famous has its benefits, but fame isn't one of them. -Larry Wall */
-----Original Message-----
From: David Crayford
Sent: Tuesday, March 24, 2020 09:03
If you eschew goto how do you deal with error handling and cleanup using
a language which doesn't support exceptions, finalization or RAII? I find
these kind of blanket rules to lead to bad code with deep nesting and useless
status variables.
--- On 2020-03-21 11:45 PM, Paul Gilmartin wrote:
> o Symbols EXPOSEd from external scopes can't be used as targets
> of ITERATE and LEAVE. (I eschew GOTO; SIGNAL is worse,)
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
