Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!linac!unixhub!slacvm!kencb
From: KENCB@SLACVM.SLAC.STANFORD.EDU
Newsgroups: comp.lang.fortran
Subject: Re: Is this kosher?
Message-ID: <91030.132436KENCB@SLACVM.SLAC.STANFORD.EDU>
Date: 30 Jan 91 21:24:36 GMT
References: <20773@hydra.gatech.EDU> <2796@dftsrv.gsfc.nasa.gov>
 <20785@hydra.gatech.EDU> <2812@dftsrv.gsfc.nasa.gov>
Organization: Stanford Linear Accelerator Center
Lines: 46

Jim Jagielski <jim@jagubox.gsfc.nasa.gov> replied:
>>In article <20785@hydra.gatech.EDU> gt4512c@prism.gatech.EDU (BRADBERRY,JOHN
L)
>>writes:
>>}In article <2796@dftsrv.gsfc.nasa.gov> jim@jagubox.gsfc.nasa.gov (Jim
>>Jagielski) writes:
>>}>In article <20773@hydra.gatech.EDU> gt4512c@prism.gatech.EDU (BRADBERRY,JOHN
>>L) writes:
>>}>}In article <2787@dftsrv.gsfc.nasa.gov> jim@jagubox.gsfc.nasa.gov (Jim
>>Jagielski) writes:
>>}>
>>}>It ain't my code... I've seen this quite a few times on VAX machines (their
>>}>FORTRAN accepts it without even a hiccup) but, of course, when porting to
>>}>other machines the code dies a horrible death. Sometimes it does make sense
>>}>to do this if the block you are referring back to is large... of course, in
>>}>that case is better to just make it "into" a subroutine and use it as such.
>>}>
    [stuff deleted]

I was very suprised at the VAX Fortran reference because ever since I first
read the VAX Fortran manual (VMS V2.1), I "knew" you weren't supposed to
jump into a IF-block.  Quoting from the current maunal (VMS V5.x, VAX
Fortran V5.x) description of Block IF Statements (Sect. 5.7.3), p 5-21:

"5.7.3.1  Statement Blocks

    A statement block can contain any executable FORTRAN statement except
    an END statement.  You can transfer control out of a statement block,
    but you must not transfer control into a block.  Thus, you must not
    transfer control from one statement block to another."

The second sentence is the relavent one.

However, MUCH to my SURPRISE, John's test program fragment compiled just
FINE under VAX Fortran!  Sheez!  I think it's time for an SPR on this...
but then I don't know the history (PDP-11 compatibility, etc.).

                         -Ken
+---------------------------------------------------------------------------+
|  Kenneth H. Fairfield         | Internet: Fairfield@Tpc.Slac.Stanford.Edu |
|  SLAC                         | DECnet:   45047::FAIRFIELD                |
|  P.O.Box 4349, Bin 98         | BITNET    Fairfield@SlacTpc               |
|  Stanford, CA   94309         | Phone:    (415) 926-2924                  |
+---------------------------------------------------------------------------+
   "These opinions are worth what you paid for 'em...
         ...and are they mine, not SLAC's, Stanford's, nor the DOE's..."