Re: Fortran vs. C (was Re: Ken & Klaus.)

From: Harry Conover (hhc314_at_yahoo.com)
Date: 09/21/04 

Date: 20 Sep 2004 17:50:36 -0700

nessuno@wigner.berkeley.edu (nessuno) wrote in message news:<f76c1166.0409201050.1d7bd2b@posting.google.com>...
> beliavsky@aol.com wrote in message news:<3064b51d.0409180938.366bc3f2@posting.google.com>...
> > nessuno@wigner.berkeley.edu (nessuno) wrote in message news:<f76c1166.0409170717.6ebe4e11@posting.google.com>...
> > > Robert Newson <ReapNewsB@bullet3.fsnet.oc.ku> wrote in message news:<414ABB87.7070100@bullet3.fsnet.oc.ku>...
> > > > Jeff Relf wrote:
> > > >
> > >
> > > <snip>
> > >
> > > I did a lot of Fortran programming, most of it Fortran 66 (!). The
> > > older Fortrans were pretty awful by today's standards of what a
> > > programming language should be. One problem in upgrading them was
> > > that you had to introduce incompatibilities with previous versions to
> > > change some things. For example, on going from Fortran 66 to Fortran
> > > 77, loop testing was moved to the start of the loop (in old Fortran,
> > > all loops would execute at least once, unless you explicitly put in a
> > > test to branch around them). I never learned Fortran 95, by then I
> > > had switched to C. But it was obvious that in order to improve
> > > Fortran 77, one would have to introduce further incompatibilities with
> > > it.
> >
> > What seems "obvious" to you is incorrect in this case. Fortran 90
> > greatly improved on Fortran 77 and maintained full backward
> > compatibility. Every standard-conforming Fortran 77 program is an F90
> > program, with the same meaning.
> >
> > > Once you've crossed this threshold, the question is, how far do
> > > you go? If you're willing to go far enough in introducing
> > > incompatibilities, you could transform Fortan exactly into C, maybe in
> > > several steps if you wanted to do that. To me it seemed pointless.
> > > Why not just use C?
> >
> > Because C is missing a lot of Fortran 95 features:
> >
> > (1) In Fortran 95, you can allocate a 3-D array with just
> >
> > real, allocatable :: x(:,:,:)
> > allocate (x(n1,n2,n3))
> >
> > The correspoding C code is longer and trickier.
> >
> > (2) Passing arrays to functions is easier, since their size can
> > queried. In Fortran you can just write
> >
> > call foo(x)
> >
> > and start subroutine foo with
> >
> > subroutine foo(x)
> > real, intent(in) :: x(:,:,:)
> > integer :: n1,n2,n3
> > n1 = size(x,1)
> > n2 = size(x,2)
> > n3 = size(x,3)
> >
> > It's not easy to write a C function taking a general 2-D or 3-D array
> > AFAIK.
> >
> > (3) Fortran 90/95 has array operations and array sections comparable
> > to Matlab, letting you write fewer lines of code which better reflect
> > the operations you are trying to perform.
> >
> > (4) When you do need loops, the Fortran DO-loop is safer than the for
> > loop of C because you are guaranteed that the loop variable does not
> > change within the loop. Usually this is what I want. If not, a
> > DO-ENDDO loop without a loop variable but with an EXIT suffices.
> >
> > (5) Until C99, which is not so widely used as C90, there are no
> > complex variables in C.
>
> Yeah, I forgot to mention, original C didn't have complex variables,
> and it would have hardly been difficult to have included them from the
> beginning. And it's a pain to work around this.
>
> Maybe if I had to do serious scientific programming again, I'd have to
> learn Fortran 95, but I'm not enthusiastic about it.
>
> Here is a question: Is there anything a general purpose programming
> language (like C) needs that a scientific programming language doesn't
> need? I don't think so, especially if you want to write large
> programs. The converse is not true, of course, there are special
> needs for scientific programs, like complex variables, and efficiency
> is paramount. So in an ideal world, we'd have just one language for
> both scientific programming and everything else.
>
> Sounds like from what you have above that Fortran 95 passes length
> arguments along with array pointers. Sort of like what PL/I used to
> do with strings (they were called "dope vectors", i.e., the structures
> containing the length and pointer to the actual string).
>
> If Fortran 95 is backward compatible, then it keeps the record
> oriented I/O, which I find very awkward after working with C.
>
> Nessuno

Amazing, stupidly I hadn't realized that Fortran was still used, given
that the last time I saw it was back around 1970! :-) Still, as a
physicist I always like it as a turn-the-crank number cruncher.

Seriously speaking though, I really don't understand how anyone
familiar with both Fortran and C can compare the two without cracking
a smile. Fortran is a high level application oriented language, while
C is a relatively low-level systems implementation language.

Comparing the two is like comparing a cash register to a traffic light
(bad analogy I know, but it is the best that I could come up with on
short notice). Still, I believe you get my point.

Comparing Fortran to C is in my mind similar to comparing Fortran to
Assembly Language, since C is only a slight step above assembly
language. C offsets this limitation by providing absolutely wonderful
data structuring and access shortcuts called (strangely enough)
pointers and structures. By contrast, navigating your way through
complex data structures in Fortran becomes a major hassle, and a great
burner of CPU time.

Then too, since each of these languages have a role in different
markets, they are rarely placed in a position of competing with one
another.

Just my thoughts...

                                                    Harry C.

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