Buddha Buck wrote:
> At 12:00 AM 9/12/00 +1100, Jeremy Howard wrote:
> >[EMAIL PROTECTED] wrote:
> >> Reading through the examples left me wondering about some
> >> technicalities:
> >>
> >> > @t[|i;|j] = @a[|j;|i]; # transpose 2-d @a
> >>
> >> Written like this it would require that @a is exact 2-dim, i.e. it
would
> >> not just swap the first two dims of any n-dim array? I suppose if I'd
> >> want that I'd write
> >>
> >> @t[|i;|j;] = @a[|j;|i;]; # trailing ';' implies there might be
> >> trailing dims
> >>
> >Not necessary. Since arrays support all the syntax of a plain old list
of
> >lists, and the |i syntax just creates an implicit loop, the example
quoted
> >from the RFC will work with other sized arrays. In fact, if it was only
2d,
> >it would more properly be:
> >
> > $t[|i;|j] = $a[|j;|i]; # transpose 2-d @a
>
<...>
>
> While something like "$t[|i;|j] = $a[|j;|i];" looks clearly like
> scalar-to-scaler assignment of 2-D array elements, something like "@p =
> $a[$k;|i]*$b[|i;$k];" isn't so clear. Multiply two scalers to get an
> array?!? In truth, it's assigning an array to an array, so there is no
> problem except appearances.
>
I don't think:
@p = $a[$k;|i]*$b[|i;$k];
is meaningful. I would have thought that the iterator indexes must appear on
_both_ sides of an expression:
$p[|i] = $a[$k;|i]*$b[|i;$k];
unless using a reduction:
$sum = reduce ^_ + ^_, $a[$k;|i]*$b[|i;$k];
That way it is easy to conceptualise the implicit loop that is being
created. However, there is an issue with the width of the implicit loop. In
the above expression I want reduce() to be sent the array of values
$a[$k;|i]*$b[|i;$k]. However, in:
$sum[|i] = reduce ^_ + ^_, $a[$k;|i]*$b[|i;$k];
I want reduce to be sent the list at each iteration of $a[$k;|i]*$b[|i;$k],
where @a and @b and both 3d arrays.
I have no idea how to do this...
