note
jeroenes
I know it's a tad late, but here is my $0.01.
To my opinion [cpan://PDL] is neglected around here,
and I know I use it too little myself.<p>
With the help of PDL I only use 43 chars for the sub,
and if I looked right, it's a record in this thread. You may
add 8 chars if you want to account for the extra 'use PDL;'
statement:
<code>
use PDL:
sub p{$t=pdl+pop;$t=$t*(pdl$_)for@_;[list$t]}
</code>
This doesn't work with arrays of unequal length, but that
wasn't in the spec.
The output:
<code>
print join " ", @{p([1..5],[1..5])};
1 4 9 16 25
</code>
BTW, [tilly], why did you name it 'polynomials'? Isn't it just
a breed of recursive vector multiplication? Do I miss something?
<p>
And, '[strict]ness' requires only 3 extra chars with
a total of 46/54 chars (54 still is the record):
<code>
sub p{my $t=pdl+pop;$t=$t*(pdl$_)for@_;[list$t]}
</code>
Jeroen<br>
<i>"We are not alone"(FZ)</i>
<b>Update</b>
Thx to [tye] I now know why [tilly] talked about polynomials.
Sorry.
If we still want a matrix-kind solution, it would be like:
<code>
A = p1'*p2;
product = crossdiags(A);
</code>
But that's difficult to code in PDL, unfortunately.
Here is my 2nd attempt, works only if poly's are equal
length (pathetic 164 chars):
<code>
sub p{$t=pdl+pop;for(@_){
my $a=outer$t,pdl+pop;
transpose($a);
my $n=-1+nelem$t;
$t=zeroes($n*2+1);
$t->slice("$_:".($_+$n))+=$a->slice("$_,:")for 0..$n;
}
[list$t]}
</code>
Will ponder it a bit more and get back....
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