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Postings from September 2000
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
> #compute pairwise sum, pairwise product, pairwise difference...
> @sum = @a[|i;|j;|k;|l] + @b[|i;|j;|k;|l];
> @prod= @a[|i;|j;|k;|l] * @b[|i;|j;|k;|l];
> @diff= @a[|i;|j;|k;|l] - @b[|i;|j;|k;|l];
Hm, not sure if I am missing the point of these examples. Is that any
different from the elementwise '+','*','-' apart from being possibly
limited to 4D arrays?
> #print lots of stuff to the screen.
> sub foo { print join(',',@_),"\n"; return 0; }
> $zero[|i;|j;|k;|l;|m;|n;|o;|p] = foo(|i,|j,|k,|l,|m,|n,|o,|p);
Should that be '$zero' or '@zero'?
>
> # Sneaky way to generate dot-product:
> my $dotproduct;
> { my @temp[|i] = $dotproduct += $a[|i] * $b[|i]; }
Hm, how can this work with lazy evaluation? How is Perl supposed to know
that @temp should be transiently created to increment $dotproduct as a
side effect? Also, doesn't the above syntax seem to be conflicting with
perl context rules since it essentially contains a statement
@arr = $scalar
Christian
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