Changeset 3ace5b6 in git

Timestamp:

Jul 24, 2012, 1:48:24 PM (12 years ago)

Author:

Martin Lee <martinlee84@…>

Branches:

(u'spielwiese', '17f1d200f27c5bd38f5dfc6e8a0879242279d1d8')

Children:

f55f3941f7a85ba15e8bc819fdb09964b90ea669

Parents:

8681bf84c636b8f6dc4a144d33450d09a28c5154

git-author:

Martin Lee <martinlee84@web.de>2012-07-24 13:48:24+02:00

git-committer:

Martin Lee <martinlee84@web.de>2012-09-04 17:25:37+02:00

Message:

chg: new command to get tail coeff wrt. given variable

Location:

factory

Files:

• canonicalform.cc (modified) (2 diffs)
• canonicalform.h (modified) (2 diffs)

factory/canonicalform.cc

@@ -478 +478 @@
 // have a taildegree larger than zero.
 //
+// tailcoeff( v ) returns the tail coefficient of CO where CO is
+// considered an univariate polynomial in the polynomial variable
+// v.
+// Note: If v is less than the main variable of CO we have to
+// swap variables which may be quite expensive.
+//
 // See also: InternalCF::tailcoeff(), InternalCF::tailcoeff(),
 // InternalPoly::tailcoeff(), InternalPoly::taildegree,
@@ -490 +496 @@
     else
         return value->tailcoeff();
+}
+
+CanonicalForm
+CanonicalForm::tailcoeff (const Variable& v) const
+{
+    if ( is_imm( value ) || value->inCoeffDomain() )
+        return *this;
+
+    Variable x = value->variable();
+    if ( v > x )
+        return *this;
+    else if ( v == x )
+        return value->tailcoeff();
+    else {
+        CanonicalForm f = swapvar( *this, v, x );
+         if ( f.mvar() == x )
+             return swapvar( f.value->tailcoeff(), v, x );
+         else
+            // v did not occur in f
+            return *this;
+    }
 }
 

factory/canonicalform.h

@@ -112 +112 @@
 
     CanonicalForm tailcoeff () const;
+    CanonicalForm tailcoeff ( const Variable & v ) const;
     int taildegree () const;
 
@@ -295 +296 @@
 tailcoeff ( const CanonicalForm & f ) { return f.tailcoeff(); }
 
+inline CanonicalForm
+tailcoeff (const CanonicalForm& f, const Variable& v) { return f.tailcoeff(v); }
+
 inline int
 level ( const CanonicalForm & f ) { return f.level(); }