Questions on reuse of FORMAT statements and newer I/O options such as ACCESS='STREAM'
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From: John on 28 Dec 2009 16:31 Thanks. Since "Format reversion always causes a new record; there are no exceptions"; backed up by your chain of standard references seems to have quelled the dissent, we will report the various deviations by some compilers as bugs. As a footnote, some of the confusion came from the f2008 section C.7.1, which uses the term "format rescan" instead of "format reversion" and, as you guessed, from extension behaviors such as "$" in a format and non-standard stream I/O behavior. Plus, not everyone had used reversion much (and some have ~50 years FORTRAN experience). On Dec 28, 12:55 am, nos...(a)see.signature (Richard Maine) wrote: > John <urbanj...(a)comcast.net> wrote: > > Anyhow, the result is we are having a local difference of opinion on > > when to expect a newline to be generated when re-using a format when a > > single non-advancing I/O and/or implied DO's write statement > > "exhausts" > > the format; ESPECIALLY if formatted stream I/O is used (in particular, > > should a WRITE(IO,*) be equivalent to calling the NEW_LINE() function > > when writing to a stream?). > > First, it makes no difference whether you are using stream or not. You > won't find a hint of any such difference anywhere in the standard. > > Stream doesn't even change the default for the advance specifier. See > 9.5.1.3 (ADVANCE= specifier in a data transfer statement) in F2003. The > last sentence is > > "If this specifier is omitted from an input/output statement that > allows the specifier, the default is YES." > > Note that there are no conditions relating to stream versus sequential. > The default is just YES. The condition about statements that allow the > specifier is for things like internal I/O. > > Second, even if one explicitly specifies ADVANCE='no', that has no > effect on reversion of format. Advancing versus non-advancing I/O > affects only whether the record is terminated at the end of the output > statement. It has no effect on new records arising from explicit "/" > edit descriptors or reversion of format (or from writing newline > characters in stream output). > > See the 3rd para after Note 10.5 in F2003. That's the para that > describes format reversion. Skipping over the bits that describe when > reversion happens and how it interacts with I/O list elements, we find > > ".. the file is positioned in a manner identical to the way it is > positioned what a slash edit descriptor is procesed..." > > Note there are no conditions relating to advance='no, stream access, or > anything of the sort. It just has the effect of a slash. Look in the > section about slash. That would be 10.7.2. Not only doesn't it exclude > stream I/O, it specifically includes it. > > "On output to a file connected for sequential or stream acess, a new > empty record is created following the current record." > > I don't see how one could plausibly misread this stuff. Now if one were > to try to just guess the behavior, or possibly extrapolate from > nonstandard extensions to f77, one might come to different conclusions. > But I don't see much wiggle room on this in the standard. > > Do note that there is a difference between format reversion (what you > are calling reuse) and just comming to the end of the i/o list. Format > reversion always causes a new record; there are no exceptions. Comming > to the end of the i/o list causes a new record depending on the setting > of advance (which does not depend on stream versus sequential). > > -- > Richard Maine | Good judgment comes from experience; > email: last name at domain . net | experience comes from bad judgment. > domain: summertriangle | -- Mark Twain |