Re: [Matlisp-users] help with gross array hack needed

[rif <ri...@MI...>]

> Not necessarily.  Displaced arrays are good for row-major slices.  So 
> if the matrix where (N + 1 x N), then you could "displace away" the 
> first row.  Unfortunately, FORTRAN is column-major.  The only way I see 
> around this is to transpose the array first, and then displace.  
> However, that may cause problems for the algorithm at hand.
> 
> Isn't this fun? :)

> Marco Antoniotti					http://bioinformatics.nyu.edu

Actually, I'm OK with row-major vs. column-major, because all my
matlisp arrays are stored as 1d column-major arrays in CL.

The real problem with displacement is that displacing a (simple-array
double-float *) produces a (vector double-float *), and therefore I
cannot write something like:

(defmethod displaced-matrix ((m real-matrix) (start-column fixnum))
  (let* ((nc (number-of-cols m))
         (nr (number-of-rows m))
         (new-columns (- nc start-column)))
    (make-instance 'real-matrix 
		   :nrows nr
		   :ncols (- nc start-column)
		   :store (make-array (* nr new-columns)
                   :element-type 'double-float
		   :displaced-to (matlisp::store m)
		   :displaced-index-offset (* nr start-column)))))

Is there any (obviously, implementation specific way) to do a
displaced (simple-array double-float *) --- this was my original
question?

Alternately, within matlisp, is there an easy way to extend (for
example) vector-data-address to work on a (simple-array double-float
*) in the right way?  Right now, it fails on the check-type, because
it requires a simple-array.

Cheers,

rif

ps.  Obviously, I can do what I want with sufficient effort.  For
instance, I could define my own interface to the Fortran functions
which take pointers directly, and then do the pointer arithmetic
myself.  This seems like a lot of work, and I'm attempting to avoid
this, though I may have to do it if there's no other way.