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source: branches/f4grobner/slow-add.lisp@ 4543

Last change on this file since 4543 was 4539, checked in by Marek Rychlik, 8 years ago

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File size: 954 bytes
Line 
1(in-package :polynomial)
2
3(defun f-add (p q order-fn add-fn)
4 "Add two polynomials, P and Q, represented as lists of terms.
5The operation is destructive to both polynomials, as the terms
6of both lists are combined into the result. The operation does not
7create any new instance of TERM."
8 (do (r)
9 ((or (endp p) (endp q))
10 ;; NOTE: R contains the result in reverse order. Can it
11 ;; be more efficient to produce the terms in correct order?
12 (unless (endp q)
13 (setf r (nreconc r q)))
14 (unless (endp p)
15 (setf r (nreconc r p)))
16 r)
17 (multiple-value-bind
18 (greater-p equal-p)
19 (funcall order-fn (car p) (car q))
20 (cond
21 (greater-p
22 (rotatef (cdr p) r p)
23 )
24 (equal-p
25 (let ((s (funcall add-fn (lc p) (lc q))))
26 (cond
27 ((universal-zerop s)
28 (setf p (cdr p))
29 )
30 (t
31 (setf (lc p) s)
32 (rotatef (cdr p) r p))))
33 (setf q (cdr q))
34 )
35 (t
36 (rotatef (cdr q) r q))))))
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