Changeset 55

Timestamp:

2015-06-05T11:18:00-07:00 (9 years ago)

Author:

Marek Rychlik

Message:

* empty log message *

File:

• branches/f4grobner/polynomial.lisp (modified) (1 diff)

branches/f4grobner/polynomial.lisp

@@ -188 +188 @@
           (coerce-coeff ring expr vars)))))))
 
-
-
+(defun spoly (ring f g)
+  "It yields the S-polynomial of polynomials F and G."
+  (declare (type poly f g))
+  (let* ((lcm (monom-lcm (poly-lm f) (poly-lm g)))
+          (mf (monom-div lcm (poly-lm f)))
+          (mg (monom-div lcm (poly-lm g))))
+    (declare (type monom mf mg))
+    (multiple-value-bind (c cf cg)
+        (funcall (ring-ezgcd ring) (poly-lc f) (poly-lc g))
+      (declare (ignore c))
+      (poly-sub 
+       ring
+       (scalar-times-poly ring cg (monom-times-poly mf f))
+       (scalar-times-poly ring cf (monom-times-poly mg g))))))
+
+
+(defun poly-primitive-part (ring p)
+  "Divide polynomial P with integer coefficients by gcd of its
+coefficients and return the result."
+  (declare (type poly p))
+  (if (poly-zerop p)
+      (values p 1)
+    (let ((c (poly-content ring p)))
+      (values (make-poly-from-termlist (mapcar
+                          #'(lambda (x)
+                              (make-term (term-monom x)
+                                         (funcall (ring-div ring) (term-coeff x) c)))
+                          (poly-termlist p))
+                         (poly-sugar p))
+               c))))
+
+(defun poly-content (ring p)
+  "Greatest common divisor of the coefficients of the polynomial P. Use the RING structure
+to compute the greatest common divisor."
+  (declare (type poly p))
+  (reduce (ring-gcd ring) (mapcar #'term-coeff (rest (poly-termlist p))) :initial-value (poly-lc p)))