I have many years' experience writing COBOL code and have used GO TO and
THRU only as a means of exiting a paragraph. I frequently code paragraph
subroutines that perform a series of related edits, and would use them like
this:
Perform 2000-Validate-Input thru 2000-exit.
* test resultant switch settings here...
2000-Validate-Input.
If some-test-here-failed
Set indicator-switch to true
Go to 2000-exit
End-if.
If some-other-test-fails
Set indicator-different-switch to true
Go to 2000-exit
End-if.
* Blah, blah, blah
* When you get here, all tests are good and action can be taken
2000-exit.
Exit.
The THRU clause is only to support an "exit paragraph" ability. Because I
follow some rules with this technique, it has never caused me a problem.
The rules? They are simple:
- Only "go to" the exit point for the current paragraph. I never span.
This means that the "go to" statements are always pointed downward - the
same way my perform statements always point.
- I verify that this rule is observed by F GO WORD in ISPF (with comments
excluded). Each time I find a GO, I then look for P'####-' 8 to ensure that
the exit paragraph is the next paragraph.
I, too, believe that "thru" and "section" is a preference that can't be
persuaded in most people. I personally hate to use sections and view them
as evil. When forced to use sections, such as when performing an internal
sort, I just code unreferenced "dummy" sections around my input and output
sections.
It would be nice if an "exit paragraph" statement existed. When it does,
I'll never need a THRU or GO TO again - and good riddance!
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