Re: Iterating over a ND-array

[David Bateman]

Søren Hauberg wrote:

> I just calculated the total number of elements and accessed them by 
> using a single index, like you suggested.
>
> Thanks,
> Søren

That's the best way to do it. You might also want to be careful whether 
the variable is "const" or not since different versions of the () 
operator are used whether the variable is const or not... The operator 
() can't tell if the variable is on the right or left hand side of an 
equation and so if the variable is not const every time you call it, it 
will check if a copy of the matrix is needed. This is why you often see 
the fortran_vec function used in octave even when a fortran function 
isn't called, as it allows this checking to be bypassed.

So in short

NDArray foo (const NDArry &m)
{
 NDArray ret (m.dims ());
 double *bar = ret.fortran_vec ();
 for (int i =0; i < m.nelem (); i++)
    bar [i] = foobar (m(i));
 return ret;
}

is good practice...

D.

--
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