Re: what's it worth to write a short program for polynomial multiplication?

On Jun 16, 11:00 am, Dan Christensen <j...@xxxxxx> wrote:
[Dan] Here's the equivalent code:

c = collections.defaultdict(int)
for ea in a:
for eb in b:
c[ea+eb] += a[ea]*b[eb]

The only cryptic line is the first, which defines a hash table
whose default value is 0.

Dan

Dan's note reminded me that there are other (in my opinion, very non-
lispy) ways of writing loops in ANSI standard Common Lisp. I rarely
use them, but they make possible the following code..


(setf ans (make-hash-table))
(loop for ea being the hash-index of a using (hash-value c1) do
(loop for eb being the hash-index of b using (hash-value c2) do
(incf (gethash (+ ea eb) ans 0) (* c1 c2))))

.

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