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From: jlg@cochiti.lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: matrix multiplication
Keywords: parameters, pass-by-value, pass-by-reference
Message-ID: <23261@lanl.gov>
Date: 6 May 91 15:20:39 GMT
References: <1991May04.170203.22222@ariel.unm.edu>
Sender: news@lanl.gov
Organization: Los Alamos National Laboratory
Lines: 19

In article <1991May04.170203.22222@ariel.unm.edu>, scavo@cie.uoregon.edu (Tom Scavo) writes:
|> [...]                         Also, does anyone know of a Fortran 
|> compiler that implements pass-by-value-result, a kind of delayed 
|> pass-by-reference where the actual parameters are updated at the 
|> point of return?  Or is this non-standard?

It is quite within the standard to pass procedure arguments by value/result.
It is also standard to pass by reference.  The reason for the Fortran 
prohibition of aliasing parameters through procedure calls is to make
the semantics of both forms of procedure call identical.  That's why
you can't do MATMLT(X,Y,X,M,N,M) - if the procedure assigns to X.  If
you were allowed to do so, the semantics of the two parameter passing
methods would be different.

Yes, you can implement Fortran with value/result parameters.  The bad
news is that it still doesn't do what you want since aliasing IN and
INOUT (or OUT) parameters is illegal.

J. Giles