Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!hc!beta!a!jlg
From: jlg@a.UUCP (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Fortran 8x, irrelevant features
Message-ID: <501@a.UUCP>
Date: 3 Mar 88 04:23:22 GMT
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 55
Keywords: Fortran, Standard


In the previous article in this series, I stated the criterion I would
use to determine desirability of new features in Fortran 8x. This was:

> The criterion for Fortran 8x features (in my opinion) should be to
> certify existing practice or to extend the language in a significant
> way.  I will use this criterion throughout this discussion.

To this criterion I would like to add the following reservation:
If a new feature costs little to implement and doesn't negatively
effect users who don't use the new feature, then I don't care whether
the new feature is included or not.

In this class of 'irrelevant' features are such things as the free source
form, DO TIMES, DO WHILE, and REPEAT UNTIL.  All these features can be
implemented with minor changes to the 'frontend' part of a compiler,
some even in the lexical scanner alone.

Clearly, people who don't use these features won't be effected at all.
The old fixed source form is not even deprecated, so continued use is
not in future danger either.

Some people have requested that the free source form be implemented only
if a filter from the old for is a required environment utility.  Why bother?
The old source form will continue to work, there is not even a need to
recode.  (Besides, a week with yacc or shorter with a more powerful tool
would suffice to write the required filter - in Fortran itself if you
want.)

If the free source form IS left in the language, it should include
significant blanks (as inter-token delimiters) and it should allow
the continuation mark (&) to appear either on the line to be continued
or on the continuing line (with both places required for continued
character constants of course).

The other features (DOs and REPEATs) are just simple translations into the
equivalent:

DO 5 TIMES   =>          DO IVAR=1,5
				! IVAR is a unique temporary integer
				! or may be implemented in whatever
				! way the compiler chooses.

DO WHILE (COND) => 1234  IF (COND) THEN
...                      ...    ! 1234 is a unique parse generated label
END DO                   GOTO 1234

REPEAT             5678  CONTINUE
...                      ...    ! 5678 is a unique parse generated label
UNTIL (COND)             IF (COND) GOTO 5678

Clearly, these feature don't add to the complexity of the compiler much,
and they OBVIOUSLY don't handicap existing users any.

J. Giles
Los Alamos