Is 'everything' a refrence or isn't it?

Dan Sommers me at
Thu Jan 5 11:23:08 EST 2006

On Thu, 05 Jan 2006 14:28:51 +0100,
David Murmann <david.murmann at> wrote:

> Dan Sommers schrieb:
>> int **_idx;
>> for( _idx = lst; _idx < lst + NLST; ++_idx ) {
>> int *i;
>> i = *_idx;
>> /* compare "the item to which i is bound" to "a constant" */
>> if( *i == *(&_i2) )
>> /* rebind i to _i4 */
>> i = &_i4;
>> }
>> for( _idx = lst; _idx < lst + NLST; ++_idx ) {
>> int *i = *_idx;
>> printf( "%d\n", *i );
>> }

For reference, Stuart Gathman's looks like this:

> > int _idx;	/* internal iterator */
> > for (_idx = 0; _idx < NLST; ++_idx) {
> >   int *i = lst[_idx];

> i don't see what is so fundamentally different in this version
> compared to the one from Stuart Gathman (except it works, but i think
> it was a typo) ...

I agree that Stuart's error was a typo.

> ... do you want to stress that python uses an iterator (if so, i would
> have renamed _idx to _iter, because it ain't not index anymore)? whats
> the point of not starting the for loop at 0? ...

I was trying to show iteration over a list of items, rather than indexed
access into a list of pointers, but it is no longer as clear to me as it
was at the time that I did a good job of that.  ;-)

Another thing I wanted to show is that no amount of changing i would
have any effect on the list, and I missed it in Stuart's code (my

Or maybe my Python/C ratio is so high that seeing a loop variable used
as an index into a list or an array just bugs me.  ;-)

_iter vs. _idx is a non-starter for me because of the baggage associated
with those words.

> ... and is there a difference between (*i == _idx) and (*i ==
> *(&_idx))?

Again, just the emphasis that the comparison is through bindings rather
than directly on the objects, to show that the bindings are completely
independent of the objects.  I am pretty sure that there is no semantic
difference between *(&_idx) and _idx in the "normal" case, but there may
be some very odd corner cases if _idx were volatile and/or delcared


Dan Sommers

More information about the Python-list mailing list