Re: Octave C++ classes

[Paul Thomas]

Tomasso,

Just to expand on David's reply:

#include <octave/oct.h>
DEFUN_DLD(revs,args,nargout," b = revs( a )\n b is the index reverse of
matrix a\
\n\nTest with b = revs( [1:5]'*[1:5] )")
{
 Matrix vin( args(0).matrix_value());
 idx_vector idxc( Range( double( vin.cols() )  , 1.0 , -1.0 ) ); 
 idx_vector idxr( Range( double( vin.rows() )  , 1.0 , -1.0 ) ); 
 return octave_value( Matrix( vin.index( idxr , idxc ) ) );
}

Does what you are trying to do.  This one inverts row and column orders.  To
reverse a vector;
{
 ColumnVector vin( args(0).vector_value());
 idx_vector idx( Range( double( vin.rows() )  , 1.0 , -1.0 ) ); 
 return octave_value( Column_Vector( vin.index( idx ) ) );
}

does the trick.

Note constructors
    Range( double begin , double limit , double increment )
    idx_vector( Range )
    Matrix( Array2<double> )  (NB.  vin.index( i , j) returns Array2 )

and function
    Matrix::index( idx_vector , idx_vector )

Best regards

Paul T  
    


David Bateman wrote:

> Check out the code in do_index_op and assign in ov-base-mat.cc where
> the class index_vector is used. The value of index_vector can be a
> ":" (flagged as a magic colon) or a range. This should do pretty 
> much what you want.
>
> As for the octave -> c++ compiler check out
>
> http://www.stud.tu-ilmenau.de/~rueckn/
>
> which is experimental..
>
> D.
>
> According to Tommaso Cucinotta <address@hidden> (on 07/08/04):
>  
>
> > Hi,
> >
> > I'd like to know if there is a "natural" way to
> > translate something like
> >
> >  X_rev = X(length(X):-1:1)
> >
> > (or making other more advanced row or column selections,
> > like 1:2:9 ecc...) into C++ using the octave classes.
> >
> > It seems to me the Range class is what I need to use, but
> > I cannot figure out how to index a vector or matrix with a
> > Range.
> >
> > Also, I would like to know if anybody ever wrote an Octave to C++
> > translator.
> >
> > Many thanks in advance,
> >
> >         Tommaso.
> >
> >
> >
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> >
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>
>  




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