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[4495] | 1 | (in-package :polynomial)
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| 2 |
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| 3 | (defun f-add (p q order-fn add-fn)
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| 4 | "Add two polynomials, P and Q, represented as lists of terms.
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| 5 | The operation is destructive to both polynomials, as the terms
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| 6 | of both lists are combined into the result. The operation does not
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| 7 | create any new instance of TERM."
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| 8 | (do (r)
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| 9 | ((or (endp p) (endp q))
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| 10 | ;; NOTE: R contains the result in reverse order. Can it
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| 11 | ;; be more efficient to produce the terms in correct order?
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| 12 | (unless (endp q)
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| 13 | (setf r (nreconc r q)))
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| 14 | (unless (endp p)
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| 15 | (setf r (nreconc r p)))
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| 16 | r)
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| 17 | (multiple-value-bind
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| 18 | (greater-p equal-p)
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| 19 | (funcall order-fn (car p) (car q))
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| 20 | (cond
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| 21 | (greater-p
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| 22 | (rotatef (cdr p) r p)
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| 23 | )
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| 24 | (equal-p
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| 25 | (let ((s (funcall add-fn (lc p) (lc q))))
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| 26 | (cond
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| 27 | ((universal-zerop s)
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| 28 | (setf p (cdr p))
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| 29 | )
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| 30 | (t
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| 31 | (setf (lc p) s)
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| 32 | (rotatef (cdr p) r p))))
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| 33 | (setf q (cdr q))
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| 34 | )
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| 35 | (t
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| 36 | (rotatef (cdr q) r q))))))
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