Changeset 057578 in git

Timestamp:

May 25, 1999, 6:49:39 PM (25 years ago)

Author:

Olaf Bachmann <obachman@…>

Branches:

(u'spielwiese', 'fe61d9c35bf7c61f2b6cbf1b56e25e2f08d536cc')

Children:

9fd5f8a67b2159d3a039d7b0b34e704f6a617dfb

Parents:

1fff4b3fea4648d7e6b6639ecde260fdd4148b06

Message:

* better implementation of pSubst


git-svn-id: file:///usr/local/Singular/svn/trunk@3051 2c84dea3-7e68-4137-9b89-c4e89433aadc

File:

• Singular/polys.cc (modified) (3 diffs)

Singular/polys.cc

@@ -2 +2 @@
 *  Computer Algebra System SINGULAR     *
 ****************************************/
-/* $Id: polys.cc,v 1.37 1999-04-30 10:39:54 obachman Exp $ */
+/* $Id: polys.cc,v 1.38 1999-05-25 16:49:39 obachman Exp $ */
 
 /*
@@ -2110 +2110 @@
 static poly pSubst1 (poly p,int n)
 {
-  poly qq,result = NULL;
-
-  while (p != NULL)
-  {
-    qq = p;
+  if (p == NULL) return NULL;
+  if (pNext(p) == NULL)
+  {
+    if (pGetExp(p, n) != 0)
+    {
+      pSetExp(p, n, 0);
+      pSetm(p);
+    }
+    return p;
+  }
+
+  int l = pLength(p) - 1;
+  poly* monoms = (poly*) Alloc(l*sizeof(poly));
+  int i;
+  
+  for (i=0; i<l; i++)
+  {
+    if (pGetExp(p, n) != 0)
+    {
+      pSetExp(p, n, 0);
+      pSetm(p);
+    }
+    monoms[i] = p;
     pIter(p);
-    qq->next = NULL;
-    pSetExp(qq,n,0);
-    pSetm(qq);
-    result = pAdd(result,qq);
-  }
-  return result;
+  }
+  if (pGetExp(p, n) != 0)
+  {
+    pSetExp(p, n, 0);
+    pSetm(p);
+  }
+  for (i = l-1; i >= 0; i--)
+  {
+    pNext(monoms[i]) = NULL;
+    p = pAdd(p, monoms[i]);
+  }
+  pTest(p);
+  Free(monoms, l*sizeof(poly));
+  return p;
+}
+
+/*3
+* substitute the n-th variable by number e in p
+* destroy p
+*/
+static poly pSubst2 (poly p,int n, number e)
+{
+  number nn, nm;
+  int exp;
+  assume( ! nIsZero(e) );
+  
+  if (p == NULL) return NULL;
+  if (pNext(p) == NULL)
+  {
+    exp = pGetExp(p, n);
+    if (exp != 0)
+    {
+      nPower(e, exp, &nn);
+      nm = nMult(nn, pGetCoeff(p));
+      pSetCoeff(p, nm);
+      nDelete(&nn);
+      pSetExp(p, n, 0);
+      pSetm(p);
+    }
+    return p;
+  }
+
+  int l = pLength(p) - 1;
+  poly* monoms = (poly*) Alloc(l*sizeof(poly));
+  int i;
+  
+  for (i=0; i<l; i++)
+  {
+    exp = pGetExp(p, n);
+    if (exp != 0)
+    {
+      nPower(e, exp, &nn);
+      nm = nMult(nn, pGetCoeff(p));
+      pSetCoeff(p, nm);
+      nDelete(&nn);
+      pSetExp(p, n, 0);
+      pSetm(p);
+    }
+    monoms[i] = p;
+    pIter(p);
+  }
+  exp = pGetExp(p, n);
+  if (exp != 0)
+  {
+    nPower(e, exp, &nn);
+    nm = nMult(nn, pGetCoeff(p));
+    pSetCoeff(p, nm);
+    nDelete(&nn);
+    pSetExp(p, n, 0);
+    pSetm(p);
+  }
+  for (i = l-1; i >= 0; i--)
+  {
+    pNext(monoms[i]) = NULL;
+    p = pAdd(p, monoms[i]);
+  }
+  Free(monoms, l*sizeof(poly));
+  pTest(p);
+  return p;
+}
+
+poly pSubst0(poly p, int n)
+{
+  spolyrec res;
+  poly h = &res;
+  pNext(h) = p;
+  
+  while (pNext(h)!=NULL)
+  {
+    if (pGetExp(pNext(h),n)!=0)
+    {
+      pDelete1(&pNext(h));
+    }
+    else
+    {
+      pIter(h);
+    }
+  }
+  pTest(pNext(&res));
+  return pNext(&res);
 }
 
@@ -2130 +2242 @@
 poly pSubst(poly p, int n, poly e)
 {
-  if ((e!=NULL)&&(pIsConstant(e))&&(nIsOne(pGetCoeff(e))))
-    return pSubst1(p,n);
+  if (e == NULL) return pSubst0(p, n);
+
+  if (pIsConstant(e))
+  {
+    if (nIsOne(pGetCoeff(e))) return pSubst1(p,n);
+    else return pSubst2(p, n, pGetCoeff(e));
+  }
 
   int exponent,i;