Here is a contrived illustration (not useful but hopefully shows the concept):

Consider a graphics system which can render triangles and quads. A
triangle would be three vertex indices and a quad would be four vertex
indices. Now imagine that we have a number of graphic entities being
manipulated - some number of arrays of triangles and/or quads - and we
want to find where a triangle came from.

Thanks,

-- 
Raul


On Thu, Oct 24, 2013 at 3:10 PM, Roger Hui <[email protected]> wrote:
> It seems inaccurate to describe the thought experiment as ignoring trailing
> fill, but I can not now articulate why I think it is inaccurate.
>
>
>
> On Thu, Oct 24, 2013 at 12:00 PM, Raul Miller <[email protected]> wrote:
>
>> The obvious downside of the thought experiment is that trailing fill is
>> ignored.
>>
>> That said, I cannot think of any computational cases where (a)
>> trailing fill is significant, and (b) it's meaningful for item/cell
>> shapes to conflict.
>>
>> --
>> Raul
>>
>> On Thu, Oct 24, 2013 at 2:54 PM, Roger Hui <[email protected]>
>> wrote:
>> > I=: 4 : '(s{."(1,c) x) i. (s{."(1,c) y) [ s=. (}.$x)>.(-c=. <:$$x){.$y'
>> >
>> > 1 2 vs. 1 2 0.  What you get now is this:
>> >
>> >    x=: 4 2$1 2
>> >    y=: 4 3$1 2 0
>> >    x i. y
>> > 4 4 4 4
>> >
>> > That is, uniformly #x if the shapes don't match.  The question is, is the
>> > thought experimental version more useful?
>> >
>> > Reshaping the item yourself.  Of course.  Or overtake yourself, or any
>> > number alternatives.  The thought experimental version hides this bit of
>> > complexity.
>> >
>> >
>> >
>> >
>> > On Thu, Oct 24, 2013 at 6:16 AM, Don Guinn <[email protected]> wrote:
>> >
>> >> I don't see much of a need for this. I can reshape the items myself if
>> >> necessary. What about the choice of the fill, particularly for numerics?
>> >> Help for i. does not say that the comparison of items is specifically
>> match
>> >> (-:), but I thought it was. Should 1 2 be considered the same as 1 2 0 ?
>> >>
>> >>    (>1 2;2 4) I (>1 3 2; 1 2 0;2 5)
>> >>
>> >> 2 0 2
>> >>
>> >>    (>1 2;2 4) i. (>1 3 2; 1 2 0;2 5)
>> >>
>> >> 2 2 2
>> >>
>> >> Got the following error for leaving the items boxed.
>> >>
>> >>    x=: ;:'zero one two five one'
>> >>
>> >>    y=: ;:'three one four one five nine'
>> >>
>> >>    x i. y
>> >>
>> >> 5 1 5 1 3 5
>> >>
>> >>    x I y
>> >>
>> >> |length error: I
>> >>
>> >> | (s{."c x)i.(s {."c y)[s=.(}.$x)>.(-c=.<:$$x){.$y
>> >>
>> >>
>> >> On Wed, Oct 23, 2013 at 2:28 PM, Roger Hui <[email protected]
>> >> >wrote:
>> >>
>> >> > Thought experiment:  What if i. does overtake on the arguments to
>> ensure
>> >> > that the item shape of the left argument matches the cell shape of the
>> >> > right argument?
>> >> >
>> >> >    I=: 4 : '(s{."c x) i. (s{."c y) [ s=. (}.$x)>.(-c=. <:$$x){.$y'
>> >> >    x=: > ;:'zero one two five one'
>> >> >    y=: > ;:'three one four one five nine'
>> >> >
>> >> >    $x
>> >> > 5 4
>> >> >    $y
>> >> > 6 5
>> >> >
>> >> >    x i. y
>> >> > 5 5 5 5 5 5
>> >> >    x I y
>> >> > 5 1 5 1 3 5
>> >> > ----------------------------------------------------------------------
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