Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!haven!adm!cmcl2!acf5!jjb3281
From: jjb3281@acf5.NYU.EDU (Thanbo)
Newsgroups: comp.lang.fortran
Subject: Re: Type punning in FORTRAN (was in C)
Summary: weve done this for years
Message-ID: <891@acf5.NYU.EDU>
Date: 18 Oct 89 23:59:15 GMT
References: <475@idacrd.UUCP> <1989Oct10.185851.6490@agate.berkeley.edu> <1131@mpx1.lanl.gov>
Organization: New York University
Lines: 20

In article <1131@mpx1.lanl.gov>, matthias@mpx1.lanl.gov (Bjorn E. Matthias, M/S H831, 7-6241 or 7-7906) writes:
> > 
> > 	result = TRANSFER(SOURCE, MOLD, SIZE) .
> 
> If I am not mistaken, then this could be previously accomplished in
> VAX FORTRAN with EQUIVALENCE between two variables of whatever types.
> I have used this often and it appears that TRANSFER is different only
> in that one truly has *two* pieces of data, two memory locations.
> Sounds like a useful function, though I do not believe it really

This sort of thing has been done for years.  We do this with a tiny
assembly-language program called MVCX(nbytes, src, dst) which simply
copies so many bytes from src to test.  It's about 12 instructions on
the S/370 machines, or 6 instructions on VAX, with error checks to 
make sure you're passing valid addresses of arguments, and a valid
length (since FORTRAN passes by reference, the function has the addresse
of the arguments available).
                                 Thanbo
                                 Information Builders Inc.
                                 jjb3281@acf5.nyu.edu