OpenEuphoria

Re: Another quick sequence feature request!

• Posted by Patrick Barnes <mrtrick at gmail.com> Sep 24, 2004
• 471 views

Will,

I think that would be a fantastic idea... and while slow in
implementation, not much slower than going the other way..

Euphoria stores sequences internally as pointers. The memory location
of a 1-d sequence contains a pointer to each element. The memory
location of a 2-d sequence contains a pointer to each sub-sequence,
each of which contains pointers to elements.

To "look at" each element of a sequence, the interpreter needs to make
1 memory look-up for each element.
In a 2-d sequence:

If we wanted to look at a "horizontal slice", we'd do 1 memory look-up
to find the sub-sequence element containing that slice. Then we'd do 1
memory look-up for each element in the slice.
Total look-ups: 1 + element_number

If we wanted to look at a "vertical slice", there's no single
sub-sequence containg that slice, each element of the slice sits in a
different sub-sequence. So, to get each element, we need to do 2
look-ups. 1 to find the sub-sequence, 1 to find the element.
Total look-ups: 2 * element_number


Depending on the size of your 2d sequence, and the rate at which data
in the sequence needs to change, you could have 2 copies of the
sequence in memory... a vertical and a horizontal copy. Every change
has to be made to both sequences.

In a few other languages, two indexes can refer to the same data...
however it's something that you *REALLY* don't want to make a mistake
with.





On Thu, 23 Sep 2004 19:42:08 -0500, William Heimbigner
<icxcnika at hotpop.com> wrote:
> 
> Hey Rob, could you implement the following:
> 
> x[*][1]
> 
> would be:
> 
> {x[1][1],x[2][1],x[3][1], etc etc etc}
> 
> I don't know what that would do to the e2c translator abilities, but it
> would be nice if its possible...
> 
> William Heimbigner
> icxcnika at hotpop.com
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> 
> 
> 



-- 
MrTrick