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From: ags@s.cc.purdue.edu (Dave Seaman)
Newsgroups: comp.lang.fortran
Subject: Re: ERR= and END=
Message-ID: <3836@s.cc.purdue.edu>
Date: 1 Mar 89 13:49:54 GMT
References: <2291@unmvax.unm.edu> <91480@sun.uucp> <3234@ttrdc.UUCP>
Reply-To: ags@s.cc.purdue.edu (Dave Seaman)
Distribution: usa
Organization: Purdue University
Lines: 40

In article <3234@ttrdc.UUCP> levy@ttrdc.UUCP (Daniel R. Levy) writes:
>In article <91480@sun.uucp>, khb%fatcity@Sun.COM (fatcity) writes:
>< 	do i = 1, max
>< 	   read(ilun,'(your format)',IOSTAT=istat) your variable list
>< 	   if (istat .EQ. EOF) then
>< 		 EXIT
>< 	   else if (istat .NE. OK) then
>< 	         call abort('your favorite abort messages',istat)
>< 	   endif
>< 	   your processing goes here
>< 	end do
>
>Nice idea, but isn't it kind of environment dependent?  Like, where does the
>value of the EOF parameter come from?

A good point.  To make it environment-independent, change the condition

	if (istat .EQ. EOF) then

to read

	if (istat .LT. 0) then

which is guaranteed to be .TRUE. if and only if an end-of-file condition
was encountered on the preceding read, because of paragraph 12.7 in the 
standard.  By the same token, the condition

	else if (istat .NE. OK) then

would be better expressed as

	else if (istat .GT. 0) then

for detecting error conditions.  This also demonstrates why end-of-file is
definitely not an error condition:  the IOSTAT= return would have to be
simultaneously positive and negative!

-- 
Dave Seaman	  					
ags@j.cc.purdue.edu