From 8fc9873ef51530768138e7a30ef56b5da659950c Mon Sep 17 00:00:00 2001
From: Michael Hemmer <hemmer@mpi-inf.mpg.de>
Date: Mon, 11 Dec 2006 11:09:30 +0000
Subject: [PATCH] default for Scalar_factor_traits

---
 .gitattributes                                |   1 +
 .../include/CGAL/Scalar_factor_traits.h       | 141 ++++++++++++++++++
 2 files changed, 142 insertions(+)
 create mode 100644 Algebraic_foundations/include/CGAL/Scalar_factor_traits.h

diff --git a/.gitattributes b/.gitattributes
index 3b1f056ec2b..46de9c1d329 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -98,6 +98,7 @@ Algebraic_foundations/include/CGAL/Fraction_traits.h -text
 Algebraic_foundations/include/CGAL/Needs_parens_as_product.h -text
 Algebraic_foundations/include/CGAL/Rational_traits.h -text
 Algebraic_foundations/include/CGAL/Real_embeddable_traits.h -text
+Algebraic_foundations/include/CGAL/Scalar_factor_traits.h -text
 Algebraic_foundations/include/CGAL/utils.h -text
 Algebraic_foundations/include/CGAL/utils_classes.h -text
 Algebraic_foundations/test/Algebraic_foundations/Algebraic_structure_traits.C -text
diff --git a/Algebraic_foundations/include/CGAL/Scalar_factor_traits.h b/Algebraic_foundations/include/CGAL/Scalar_factor_traits.h
new file mode 100644
index 00000000000..8d6bcd27851
--- /dev/null
+++ b/Algebraic_foundations/include/CGAL/Scalar_factor_traits.h
@@ -0,0 +1,141 @@
+// ============================================================================
+//
+// Copyright (c) 2001-2006 Max-Planck-Institut Saarbruecken (Germany).
+// All rights reserved.
+//
+// TODO: Add licence
+//
+// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
+// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+//
+// $URL: $
+// $Id: $
+// 
+//
+// Author(s)     : Arno Eigenwillig <arno@mpi-inf.mpg.de>
+//                 Michael Hemmer   <mhemmer@uni-mainz.de>
+//
+// ============================================================================
+
+// TODO: The comments are all original EXACUS comments and aren't adapted. So
+//         they may be wrong now.
+
+#ifndef CGAL_SCALAR_FACTOR_TRAITS_H
+#define CGAL_SCALAR_FACTOR_TRAITS_H
+
+#include <CGAL/Algebraic_structure_traits.h>
+
+/*! \file NiX/Scalar_factor_traits.h
+ *  \brief Definition of traits class NiX::Scalar_factor_traits.
+ */
+CGAL_BEGIN_NAMESPACE
+
+/*! \nosubgrouping
+ *  \ingroup NiX_Scalar_factor_traits_spec
+ *  \brief traits class for scalar factor extraction
+ *  
+ *  A model of the concept ScalarFactorTraits. 
+ * 
+ *  This is the default implementation of NiX::Scalar_factor_traits. 
+ *  It is valid for most basic number types as Integer, Rational etc. 
+ */
+template< class NT_ >
+class Scalar_factor_traits {
+  public:
+    // the supported number type
+    typedef NT_ NT;
+    // NT is also 
+    typedef NT Scalar;
+
+    // functor computing the scalar factor of a basic number type. 
+    class Scalar_factor {
+        static Scalar scalar_factor(const NT& a, Integral_domain_tag) {
+            typename Algebraic_structure_traits<NT>::Unit_part upart;
+            typename Algebraic_structure_traits<NT>::Integral_division idiv;
+            return idiv(a, upart(a));
+        }
+        static Scalar scalar_factor(const NT& a, Field_tag) {
+            return (a == NT(0)) ? NT(0) : NT(1);
+        }
+        static Scalar scalar_factor(const NT& a, 
+                                    const Scalar& d,
+                                    Integral_domain_tag) {
+            return Scalar(1);
+        }
+        static Scalar scalar_factor(const NT& a, 
+                                    const Scalar& d,
+                                    Field_tag) {
+            return (a == NT(0) && d == Scalar(0)) ? NT(0) : NT(1);
+        }
+        static Scalar scalar_factor(const NT& a, 
+                                    const Scalar& d,
+                                    Unique_factorization_domain_tag) { 
+            if( d == Scalar(0)) {
+                return a;
+            } else {
+                typename Algebraic_structure_traits<NT>::Gcd gcd;
+                return gcd(a,d);
+            }
+        }
+    public: 
+        // argument type
+        typedef NT argument_type;
+        // first argument type
+        typedef NT first_argument_type;
+        // second argument type
+        typedef Scalar second_argument_type;
+        // result type
+        typedef Scalar result_type;
+  
+        // determine extractable scalar factor
+        Scalar operator () (const NT& a) {
+            BOOST_STATIC_ASSERT(( ::boost::is_same< NT,Scalar >::value));  
+            typedef typename Algebraic_structure_traits<NT>::Algebraic_categrory SAT;
+            return scalar_factor(a, SAT());
+        }
+        // determine extractable scalar factor
+        Scalar operator () (const NT& a, const Scalar& d) {     
+            BOOST_STATIC_ASSERT(( ::boost::is_same< NT,Scalar >::value));  
+            typedef typename Algebraic_structure_traits<NT>::Algebraic_category SAT;
+            return scalar_factor(a,d,SAT());
+        }
+    };
+
+    class Scalar_div {
+    public:
+        // first argument type
+        typedef NT& first_argument_type;
+        // second argument type
+        typedef Scalar second_argument_type;
+        // result type
+        typedef void result_type;
+        // divide \a a in place by scalar factor \a b
+        void operator () (NT& a, const Scalar& b) {
+            CGAL_precondition(b != Scalar(0));
+            typename Algebraic_structure_traits<NT>::Integral_division idiv;
+            a = idiv(a, b);
+        }
+    };
+};
+
+/*! \ingroup NiX_Scalar_factor_traits
+ *  \brief removes the scalar factor
+ * 
+ *   Removes the scalar factor provided by NiX::Scalar_factor_traits
+ */
+template <class NT>
+void remove_scalar_factor(NT& x){
+    typedef CGAL::Scalar_factor_traits<NT> SFT;
+    typedef typename SFT::Scalar Scalar;
+    typename SFT::Scalar_factor sfac;
+    typename SFT::Scalar_div    sdiv;
+    
+    Scalar scalar=sfac(x);
+    if(scalar != Scalar(0))
+        sdiv(x,scalar);
+}
+
+CGAL_END_NAMESPACE
+
+#endif // NiX_SCALAR_FACTOR_TRAITS_H
+// EOF