Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.uucp (Richard A. O'Keefe)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran vs C for computations
Message-ID: <368@quintus.UUCP>
Date: 8 Sep 88 10:16:21 GMT
References: <362@quintus.UUCP> <3292@lanl.gov>
Sender: news@quintus.UUCP
Reply-To: ok@quintus.UUCP (Richard A. O'Keefe)
Organization: Quintus Computer Systems, Inc.
Lines: 49

In article <3292@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>From article <362@quintus.UUCP>, by ok@quintus.UUCP (Richard A. O'Keefe):
>> In article <3256@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>>>Anything C can do portably with library routines, Fortran can also do
>>>portably with library routines.
>> 
>> I would like to see a more convincing proof of this.
>
>Ok.  Take the C library.  Write bridge routines through which Fortran
>programs can call all the procedures in the C library.  Fortran now has
>a library with the same functionality as the C library.  QED  
>
>Obviously - Anything C can do portably with library routines, Fortran
>can also do portably with library routines.  This is because Fortran
>and C can both use the _SAME_ library on any given machine.
>

Sorry, this proof won't go through.  It is only the case that Fortran
and C can use the same library if they use sufficiently compatible
calling sequences and memory management strategies.  There are quite a
few other potential problems.  For example, suppose the C library routines
require that the program execute a C initialisation routine ("crt0.o")
and Fortran requires a Fortran initialisation which is incompatible with
the C one?  This is not a theoretical case!  There are far too many UNIX
systems where mixing Fortran and C code *sometimes* works provided e.g.
that you don't do any Fortran I/O if the main program is C.

As an example of another kind of difficulty, consider the System V
"ftw" function:
	int ftw(char *path,
		int (*fn)(char *, struct stat *, int),
		int depth)
Because the function parameter can call ftw() itself, and because it
can call longjmp(), I believe that it is impossible to write a
bridging routine to permit Fortran to call this, unless you modify
the C library.

>> How come _the_ language for floating-point calculations doesn't have
>> a portable way of catching or suppressing floating-point exceptions?
>
>Because no two machines have the same exception handling capabilities!
>Fortran doesn't include [them] because there is no portable
>way to implement them.

If a machine doesn't provide a way of detecting and reporting floating-
point exceptions (that is, if it insists on its right to produce
incorrect answers without notice) why should I *care* about having
Fortran on it?  Or were the numerical analysts who contributed to the
development of the IEEE 754 standard wrong in thinking this was important?