In defense of Visual Basic (was Re: Why Python does *SLICING* theway it does??)

[Fredrik Lundh]

"beliavsky at aol.com" wrote:

> Sub print_matrix(xmat() As Double)
> Debug.Print UBound(xmat, 1), UBound(xmat, 2)
> 'do stuff with xmat
> End Sub
> 
> It is trivial to allocate and pass multidimensional arrays in VBA, but
> C requires expertise with pointers. The subroutine print_matrix can
> query the dimensions of xmat, so they don't need to be passed as
> separate arguments, as in C. The fact that is tricky to do simple
> things is a sign of the poor design of C

Sounds more like poor C skills on your part.   Here's a snippet from the Python
Imaging Library which takes a 2D array (im) and creates another one (imOut).

Imaging
ImagingRankFilter(Imaging im, int size, int rank)
{
    Imaging imOut = NULL;
    int x, y;
    int i, margin, size2;

    /* check image characteristics */
    if (!im || im->bands != 1 || im->type == IMAGING_TYPE_SPECIAL)
        return (Imaging) ImagingError_ModeError();

    /* check size of rank filter */
    if (!(size & 1))
        return (Imaging) ImagingError_ValueError("bad filter size");

    size2 = size * size;
    margin = (size-1) / 2;

    if (rank < 0 || rank >= size2)
        return (Imaging) ImagingError_ValueError("bad rank value");

    /* create output image */
    imOut = ImagingNew(im->mode, im->xsize - 2*margin, im->ysize - 2*margin);
    if (!imOut)
        return NULL;

    ... actual algorithm goes here ...

    return imOut;
}

The "im" input object carries multidimensional data, as well as all other properties
needed to describe the contents.  There are no separate arguments for the image
dimensions, nor any tricky pointer manipulations.  A Python version of this wouldn't
be much different.

</F>