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From: bv <bvoh@sdynamix.com>
Subject: F9X twister & ADA (was: n-dim'l vectors)
Date: 2000/04/06
Message-ID: <38ED4ECA.ADB698C9@sdynamix.com>#1/1
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References: <8cctts$ujr$1@nnrp1.deja.com> <38EA0440.1ECBC158@ncep.noaa.gov>
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Newsgroups: comp.lang.fortran,comp.lang.ada
Date: 2000-04-07T02:59:32+00:00
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Paul van Delst wrote:
> 
> nsavvinv2@my-deja.com wrote:
> > Can a function return an n-dimensional vector?
> 
> Sure - in f90 at least....dunno about f77. I got it to work for vectors
> by using INTERFACE blocks in the code that calls the function, e.g.
> 
> FUNCTION my_func ( x, y ) RESULT ( z )
> 
>   IMPLICIT NONE
>   INTEGER, INTENT( IN ), DIMENSION( : )         :: x, y
>   INTEGER,               DIMENSION( SIZE( x ) ) :: z
> 
>   z(:) = x(:) + y(:)   ! Assumes x and y are the same size
> 
>   RETURN
> 
> END FUNCTION my_func
> 
> and then in the calling program:
> 
> PROGRAM blah
> 
>   IMPLICIT NONE
> 
>   INTERFACE
> !   Interface body for my_func
>     FUNCTION my_func ( x, y ) RESULT ( z )
>       IMPLICIT NONE
>       INTEGER, INTENT( IN ), DIMENSION( : )         :: x, y
>       INTEGER,               DIMENSION( SIZE( x ) ) :: z
>     END FUNCTION my_func
>   END INTERFACE
> 
>   INTEGER, DIMENSION( 5 ) :: x = (/ -1,  1, -1,  1 /), &
>                              y = (/  1, -1,  1, -1 /)
> 
>   WRITE( *, '( 5i5 )' ) my_func( x, y )
> 
> END PROGRAM blah


What a slaughter of Fortran, showing every symptom of design by ignorant
and incompetent committee. What happened, where they too busy with
themselves to bother and learn from ADA?? If they did, they'd see
something along these lines:

	function normalize(v: in vector) return vector is
	vni: float;
	begin
	  vni := 1./norm(v)
	  return (v(x)*vni, v(y)*vni, v(z)*vni);
	end normalize;

--	somewhere in your code   
	u,v: vector;
		.
		.
		.
	u := normalize(v);

The difference speaks for itself!! My advise to Fortran committee is to
head F9X for the nearest trash bin and start raising funds to compensate
the vendors for costs incurred to implement their vision of language
abuse.

btw, note a duality of the ADA & F77 fcn. A similar extension for
returning user types couldn't be crafted? But one would have to be aware
of the prior art of course...

--
Dr.B.Voh
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