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From: schmidtg@iccgcc.decnet.ab.com
Newsgroups: comp.lang.fortran
Subject: Re: Re: Is this kosher?
Message-ID: <3785.27ddfb30@iccgcc.decnet.ab.com>
Date: 13 Mar 91 15:13:04 GMT
Lines: 89

In article <1991Mar6.154720.1162@sbcs.sunysb.edu>, mlubran@csws5.ic.sunysb.edu (Michael J Lubrano) writes:
>>In article <2787@dftsrv.gsfc.nasa.gov> jim@jagubox.gsfc.nasa.gov (Jim Jagielski) writes:
>>>[ommitted stuff]
>>>	.
>>>	if (value .lt. 0) then
>>>	   .
>>>	else
>>>22	   do something
>>>	   .
>>>	end if
>>>	.
>>>	if (a.lt.b) goto 22
>>>
>>>Is the above legal and acceptable... I can't find any references to it in my
>>>books...
>>
> 
> A much better way to write this would be:
> 
> 10     IF (VAL.LT.0)THEN
>         .
>        ELSE
> C       DO SOMETHING
>         .
>        END IF
>         .
> C    FORCE PROGRAM FLOW
>        IF(A.LT.B)THEN
>         VAL=100
>         GO TO 10
>        END IF
> 
> setting VAL greater than 0 forces the conditional (VAL.LT.0)
> to defualt to the else, which is exactly where you want to be.
> 
> Q.E.D
> 
> 
> Mike Lubrano

Hmmm... looks like an infinite loop to me unless "do something" has an
additional side effect of forcing (a .ge. b)!!!  In general, you don't
want to change control flow in your program by forcing variables to
assume bogus values.  Too many side effects, and what if you want to
reuse that variable later on?

 Here is how I would approach the problem.

	.
	if (value .lt. 0) then
	  .
	  limit = 0
	else
	  limit = 1
	end if

	if (a .lt. b)
	  limit = limit + 1
	end if

	do 22 i = 1,limit
	  do something
22	continue	


-or- better still...

	.
	if (value .lt. 0) then
	   .
	else
	   call do_something()
	   .
	end if
	.
	if (a .lt. b) then
	   call do_something()
	end if

--

=============================================================================
Greg Schmidt -> schmidtg@iccgcc.decnet.ab.com
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