Changeset 02d009 in git for libpolys/polys/monomials/p_polys.cc

Timestamp:

Feb 15, 2021, 6:01:06 PM (3 years ago)

Author:

Hans Schoenemann <hannes@…>

Branches:

(u'spielwiese', '17f1d200f27c5bd38f5dfc6e8a0879242279d1d8')

Children:

7b5b095ed2434be9e1783ac23414e01c2a75fec4

Parents:

e6f77c64ad84a4393b83a375b4207c80fe495718

Message:

add: p_Content_n

File:

• libpolys/polys/monomials/p_polys.cc (modified) (1 diff)

libpolys/polys/monomials/p_polys.cc

@@ -2337 +2337 @@
 }
 
+void p_Content_n(poly ph, number &c,const ring r)
+{
+  if (ph==NULL)
+  {
+    c=n_Init(1,r->cf);
+    return;
+  }
+  const coeffs cf=r->cf;
+  if (pNext(ph)==NULL)
+  {
+    c=pGetCoeff(ph);
+    p_SetCoeff0(ph,n_Init(1,cf),r);
+  }
+  if ((cf->cfSubringGcd==ndGcd)
+  || (cf->cfGcd==ndGcd)) /* trivial gcd*/
+  {
+    c=n_Init(1,r->cf);
+    return;
+  }
+  number h;
+  if ((rField_is_Q(r))
+  || (rField_is_Q_a(r))
+  || (rField_is_Zp_a)(r)
+  || (rField_is_Z(r))
+  )
+  {
+    h=p_InitContent(ph,r); /* first guess of a gcd of all coeffs */
+  }
+  else
+  {
+    h=n_Copy(pGetCoeff(ph),cf);
+  }
+  poly p;
+  if(n_IsOne(h,cf))
+  {
+    goto content_finish;
+  }
+  p=ph;
+  // take the SubringGcd of all coeffs
+  while (p!=NULL)
+  {
+    n_Normalize(pGetCoeff(p),cf);
+    number d=n_SubringGcd(h,pGetCoeff(p),cf);
+    n_Delete(&h,cf);
+    h = d;
+    if(n_IsOne(h,cf))
+    {
+      goto content_finish;
+    }
+    pIter(p);
+  }
+  // if found<>1, divide by it
+  p = ph;
+  while (p!=NULL)
+  {
+    number d = n_ExactDiv(pGetCoeff(p),h,cf);
+    p_SetCoeff(p,d,r);
+    pIter(p);
+  }
+content_finish:
+  c=h;
+  // and last: check leading sign:
+  if(!n_GreaterZero(pGetCoeff(ph),r->cf))
+  {
+    c = n_InpNeg(c,r->cf);
+    ph = p_Neg(ph,r);
+  }
+}
+
 #define CLEARENUMERATORS 1