From 0d6c8786735af5d13a87957af0b36e554f39acba Mon Sep 17 00:00:00 2001
From: Guido Kanschat <dr.guido.kanschat@gmail.com>
Date: Mon, 28 May 2001 11:27:22 +0000
Subject: [PATCH] Legendre polynomials fixed

git-svn-id: https://svn.dealii.org/trunk@4734 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/base/include/base/polynomial.h | 22 +++++++++++++++++++++-
 deal.II/base/source/legendre.cc        | 10 ++++++----
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/deal.II/base/include/base/polynomial.h b/deal.II/base/include/base/polynomial.h
index 5153321895..b520904bbc 100644
--- a/deal.II/base/include/base/polynomial.h
+++ b/deal.II/base/include/base/polynomial.h
@@ -43,7 +43,7 @@ class Polynomial : public Subscriptor
 				      * of the array denotes the
 				      * constant term, the second the
 				      * linear one, and so on. The
-				      * order of the polynomial
+				      * degree of the polynomial
 				      * represented by this object is
 				      * thus the number of elements in
 				      * the @p{coefficient} array
@@ -85,6 +85,17 @@ class Polynomial : public Subscriptor
     void value (const number         x,
 		std::vector<number> &values) const;
 
+				     /**
+				      * Degree of the polynomial. This
+				      * is the degree reflected by the
+				      * number of coefficients
+				      * provided by the
+				      * constructor. Leading non-zero
+				      * coefficients are not treated
+				      * separately.
+				      */
+    unsigned int degree () const;
+    
 				     /**
 				      * Exception
 				      */
@@ -214,5 +225,14 @@ class Legendre : public Polynomial<number>
 };
 
 
+template <typename number>
+inline
+unsigned int
+Polynomial<number>::degree () const
+{
+  Assert (coefficients.size()>0, ExcVoidPolynomial());
+  return coefficients.size() - 1;
+}
+
 #endif
 
diff --git a/deal.II/base/source/legendre.cc b/deal.II/base/source/legendre.cc
index cc3c975d44..81c74a4a41 100644
--- a/deal.II/base/source/legendre.cc
+++ b/deal.II/base/source/legendre.cc
@@ -91,15 +91,17 @@ Legendre<number>::compute_coefficients (const unsigned int k)
 
 	  std::vector<number> *ck = new std::vector<number>(k+1);
 	  
-	  const number a = 1./k+1;
-	  const number b = a*(2*k+1);
+	  const number a = 1./(k);
+	  const number b = a*(2*k-1);
+	  const number c = a*(k-1);
 	  
 	  (*ck)[k]   = b*(*coefficients[k-1])[k-1];
 	  (*ck)[k-1] = b*(*coefficients[k-1])[k-2];
 	  for (unsigned int i=1 ; i<= k-2 ; ++i)
 	    (*ck)[i] = b*(*coefficients[k-1])[i-1]
-		       - k*a*(*coefficients[k-2])[i];
-	  (*ck)[0]   = -k*a*(*coefficients[k-2])[0];
+		       -c*(*coefficients[k-2])[i];
+
+	  (*ck)[0]   = -c*(*coefficients[k-2])[0];
 
 					   // finally assign the newly
 					   // created vector to the
-- 
2.39.5