diff --git a/Arithmetic_kernel/include/CGAL/CORE_arithmetic_kernel.h b/Arithmetic_kernel/include/CGAL/CORE_arithmetic_kernel.h
index 5df573c77de..3fc908252ac 100644
--- a/Arithmetic_kernel/include/CGAL/CORE_arithmetic_kernel.h
+++ b/Arithmetic_kernel/include/CGAL/CORE_arithmetic_kernel.h
@@ -54,7 +54,7 @@ public:
 
 };
 
-
+#if 0
 template <>
 struct Get_arithmetic_kernel<CORE::BigInt>{
   typedef CORE_arithmetic_kernel Arithmetic_kernel;
@@ -63,6 +63,8 @@ template <>
 struct Get_arithmetic_kernel<CORE::BigRat>{
   typedef CORE_arithmetic_kernel Arithmetic_kernel;
 };
+#endif
+
 template <>
 struct Get_arithmetic_kernel<CORE::Expr>{
   typedef CORE_arithmetic_kernel Arithmetic_kernel;
@@ -74,6 +76,7 @@ struct Get_arithmetic_kernel<CORE::BigFloat>{
 
 } //namespace CGAL
 
+
 #endif // CGAL_USE_CORE
 
 #endif //  CGAL_CORE_ARITHMETIC_KERNEL_H
diff --git a/CGAL_Core/include/CGAL/CORE/BigFloat.h b/CGAL_Core/include/CGAL/CORE/BigFloat.h
index 97183f63e50..c5df8cb8134 100644
--- a/CGAL_Core/include/CGAL/CORE/BigFloat.h
+++ b/CGAL_Core/include/CGAL/CORE/BigFloat.h
@@ -59,7 +59,7 @@ public:
   /// constructor for <tt>const char* </tt>(default base = 10)
   BigFloat(const char* s) : RCBigFloat(new BigFloatRep(s)) {}
   /// constructor for <tt>std::string</tt>(default base = 10)
-  BigFloat(const std::string& s) : RCBigFloat(new BigFloatRep(s)) {}
+  BigFloat(const std::string& s) : RCBigFloat(new BigFloatRep(s.c_str())) {}
 
   /// constructor for <tt>int</tt> and <tt>long</tt>
   //     This is a hack because in Sturm, we need to approximate any
@@ -614,11 +614,23 @@ inline BigFloat gcd(const BigFloat& a, const BigFloat& b) {
   //mpz_tdiv_qr(q.get_mp(), r.get_mp(), a.get_mp(), b.get_mp());
 //}//
 
-
+/* AF
 // constructor BigRat from BigFloat
 inline BigRat::BigRat(const BigFloat& f) : RCBigRat(new BigRatRep()){
   *this = f.BigRatValue();
 }
+*/
+
+  double doubleValue(const BigFloat& bf)
+  {
+    return bf.doubleValue();
+  }
+
+  long longValue(const BigFloat& bf)
+  {
+    return bf.longValue();
+  }
+
 } //namespace CORE
 
 #ifdef CGAL_HEADER_ONLY
diff --git a/CGAL_Core/include/CGAL/CORE/BigFloat_impl.h b/CGAL_Core/include/CGAL/CORE/BigFloat_impl.h
index 4663d7d9251..3230bc8a1ab 100644
--- a/CGAL_Core/include/CGAL/CORE/BigFloat_impl.h
+++ b/CGAL_Core/include/CGAL/CORE/BigFloat_impl.h
@@ -870,7 +870,7 @@ BigFloatRep::toDecimal(unsigned int width, bool Scientific) const {
     M <<= e2;         // M = x * 2^(e2)
   }
 
-  std::string decRep = M.get_str();
+  std::string decRep = M.convert_to<std::string>();
   // Determine the "significant part" of this string, i.e. the part which
   // is guaranteed to be correct in the presence of error,
   // except that the last digit which might be subject to +/- 1.
diff --git a/CGAL_Core/include/CGAL/CORE/BigInt.h b/CGAL_Core/include/CGAL/CORE/BigInt.h
index 44be47eeb1c..02e0645c4c2 100644
--- a/CGAL_Core/include/CGAL/CORE/BigInt.h
+++ b/CGAL_Core/include/CGAL/CORE/BigInt.h
@@ -30,6 +30,176 @@
 #include <CGAL/CORE/MemoryPool.h>
 #include <string>
 
+#if 1
+
+namespace CORE {
+
+#ifdef CGAL_CORE_USE_GMP_BACKEND
+  typedef boost::multiprecision::mpz_int BigInt;
+#else
+  typedef  boost::multiprecision::cpp_int BigInt;
+#endif
+
+
+inline int cmp(const BigInt& x, const BigInt& y) {
+  return x.compare(y);
+}
+
+
+  int set_str(BigInt& a, const char* s) {
+      // AF   makeCopy();
+    a = BigInt(s);
+    return 0;  // should be -1 if not correct in the base (we ignore)
+  }
+
+  /// longValue
+inline long longValue(const BigInt& a) {
+  return a.convert_to<long>();;
+}
+
+  /// doubleValue
+inline double doubleValue(const BigInt& a) {
+  return a.convert_to<double>();;
+}
+
+  /// isEven
+inline bool isEven(const BigInt& z) {
+  return bit_test(z,0) == 0;
+}
+/// isOdd
+inline bool isOdd(const BigInt& z) {
+  return bit_test(z,0) == 1;
+}
+
+  inline bool isDivisible(const BigInt& x, const BigInt& y) {
+    BigInt q, r;
+    divide_qr(x, y, q, r);
+    return r.is_zero();
+}
+
+inline bool isDivisible(int x, int y) {
+  return x % y == 0;
+}
+
+inline bool isDivisible(long x, long y) {
+  return x % y == 0;
+
+}
+  /// get exponent of power 2
+inline unsigned long getBinExpo(const BigInt& z) {
+    if (z.is_zero()) {
+        return (std::numeric_limits<unsigned long>::max)();
+    }
+    return lsb(abs(z));
+}
+
+  // bit length
+inline int bitLength(const BigInt& a) {
+    if (a.is_zero()) {
+        return 0;
+    }
+  return msb(abs(a))+1;
+}
+
+/// floorLg -- floor of log_2(a)
+/** Convention: a=0, floorLg(a) returns -1.
+ *  This makes sense for integer a.
+ */
+inline long floorLg(const BigInt& a) {
+  return (sign(a) == 0) ? (-1) : (bitLength(a)-1);
+}
+
+
+/// div_rem
+inline void div_rem(BigInt& q, BigInt& r, const BigInt& a, const BigInt& b) {
+  // AF q.makeCopy();
+  // AF r.makeCopy();
+  divide_qr(a, b, q, r);
+}
+
+
+  /// ulongValue
+inline unsigned long ulongValue(const BigInt& a) {
+    assert(a >= BigInt(0));
+  return a.convert_to<unsigned long>();
+}
+
+  /// exact div
+inline void divexact(BigInt& z, const BigInt& x, const BigInt& y) {
+  // AF z.makeCopy();
+  BigInt r;
+  divide_qr(x, y, z, r );  // was void mpz_divexact (mpz_t q, const mpz_t n, const mpz_t d)   Is this faster?
+  assert(r.is_zero());
+}
+
+// Chee (1/12/2004)   The definition of div_exact(x,y) next
+//   ensure that in Polynomials<NT> works with both NT=BigInt and NT=int:
+inline BigInt div_exact(const BigInt& x, const BigInt& y) {
+  BigInt z;             // precodition: isDivisible(x,y)
+  divexact(z, x, y); // z is set to x/y;
+  return z;
+}
+
+inline int div_exact(int x, int y) {
+  return x/y;  // precondition: isDivisible(x,y)
+}
+
+inline long div_exact(long x, long y) {
+  return x/y;  // precondition: isDivisible(x,y)
+}
+
+
+/// ceilLg -- ceiling of log_2(a) where a=BigInt, int or long
+/** Convention: a=0, ceilLg(a) returns -1.
+ *  This makes sense for integer a.
+ */
+inline long ceilLg(const BigInt& a) {
+  if (sign(a) == 0)
+    return -1;
+  unsigned long len = bitLength(a);
+
+  return (lsb(abs(a)) == len - 1) ? (len - 1) : len;
+}
+
+inline long ceilLg(long a) { // need this for Polynomial<long>
+  return ceilLg(BigInt(a));
+}
+
+inline long ceilLg(int a) { // need this for Polynomial<int>
+  return ceilLg(BigInt(a));
+}
+
+
+/// negate
+inline void negate(BigInt& a) {
+  // AF a.makeCopy();
+  a= - a;
+}
+
+/// get exponent of power k
+inline void getKaryExpo(const BigInt& z, BigInt& m, int& e, unsigned long uk) {
+    BigInt k(uk), q, r;
+    e = 0;
+    m = z;
+    // AF m.makeCopy();
+    for(;;) {
+        divide_qr(m, k, q, r);
+        if (!r.is_zero()) break;
+        m = q;
+        ++e;
+    }
+}
+
+  inline void power(BigInt& c, const BigInt& a, unsigned long ul) {
+    // AF c.makeCopy();
+  c = pow(a, ul);
+}
+
+} // namespace CORE
+
+#else
+
+
 namespace CORE {
 
 #ifdef CGAL_CORE_USE_GMP_BACKEND
@@ -55,11 +225,7 @@ public:
     : mp(c)
     {}
 
-  BigIntRep(const char* s, int base=0)
-    : mp(s)
-    { assert(base == 0); }
-
-  BigIntRep(const std::string& s, int base=0)
+  BigIntRep(const std::string& s)
     : mp(s)
     {}
 
@@ -118,10 +284,9 @@ public:
   BigInt(float x) : RCBigInt(new BigIntRep(x)) {}
   /// constructor for <tt>double</tt>
   BigInt(double x) : RCBigInt(new BigIntRep(x)) {}
-  /// constructor for <tt>const char*</tt> with base
-  BigInt(const char* s, int base=0) : RCBigInt(new BigIntRep(s, base)) {}
-  /// constructor for <tt>std::string</tt> with base
-  BigInt(const std::string& s, int base=0) : RCBigInt(new BigIntRep(s, base)) {}
+
+  /// constructor for <tt>std::string</tt>
+  BigInt(const std::string& s) : RCBigInt(new BigIntRep(s)) {}
 
   /// constructor for <tt>mpz_srcptr</tt>
   // explicit BigInt(mpz_srcptr z) : RCBigInt(new BigIntRep(z)) {}
@@ -254,13 +419,13 @@ public:
   /// \name String Conversion Functions
   //@{
   /// set value from <tt>const char*</tt>
-  int set_str(const char* s, int base = 0) {
+  int set_str(const char* s) {
     makeCopy();
     get_mp() = Z(s);
     return 0;  // should be -1 if not correct in the base (we ignore)
   }
   /// convert to <tt>std::string</tt>
-  std::string get_str(int base = 10) const {
+  std::string get_str() const {
     return get_mp().convert_to<std::string>();
   }
   //@}
@@ -443,7 +608,7 @@ inline double doubleValue(const BigInt& a) {
 
 void readFromFile(BigInt& z, std::istream& in, long maxLength = 0);
 /// write to file
-void writeToFile(const BigInt& z, std::ostream& in, int base=10, int charsPerLine=80);
+void writeToFile(const BigInt& z, std::ostream& in, int charsPerLine=80);
 //@}
 */
 
@@ -483,8 +648,8 @@ inline void getKaryExpo(const BigInt& z, BigInt& m, int& e, unsigned long uk) {
 
 /// divisible(x,y) = "x | y"
 inline bool isDivisible(const BigInt& x, const BigInt& y) {
-    BigInt z, r;
-    divide_qr(x.get_mp(), y.get_mp(), z.get_mp(), r.get_mp());
+    BigInt q, r;
+    divide_qr(x.get_mp(), y.get_mp(), q.get_mp(), r.get_mp());
     return r.get_mp().is_zero();
 }
 
@@ -538,7 +703,7 @@ inline void div_rem(BigInt& q, BigInt& r, const BigInt& a, const BigInt& b) {
 /// power
 inline void power(BigInt& c, const BigInt& a, unsigned long ul) {
   c.makeCopy();
-  c.get_mp() = pow(a.get_mp(), ul);
+  //c.get_mp() = pow(a.get_mp(), ul);
 }
 
 // pow
@@ -553,7 +718,7 @@ inline int bitLength(const BigInt& a) {
     if (a.get_mp().is_zero()) {
         return 0;
     }
-  return msb(abs(a.get_mp()))+1;    /// AF todo     was    mpz_sizeinbase(a.get_mp(), 2);
+  return msb(abs(a.get_mp()))+1;
 }
 
 /// floorLg -- floor of log_2(a)
@@ -590,4 +755,6 @@ inline long ceilLg(int a) { // need this for Polynomial<int>
 
 } //namespace CORE
 
+#endif
+
 #endif // _CORE_BIGINT_H_
diff --git a/CGAL_Core/include/CGAL/CORE/BigRat.h b/CGAL_Core/include/CGAL/CORE/BigRat.h
index 1cab0679018..cd4747303d9 100644
--- a/CGAL_Core/include/CGAL/CORE/BigRat.h
+++ b/CGAL_Core/include/CGAL/CORE/BigRat.h
@@ -27,6 +27,26 @@
 
 #include <CGAL/CORE/BigInt.h>
 
+#if 1
+namespace CORE {
+#ifdef CGAL_CORE_USE_GMP_BACKEND
+  typedef boost::multiprecision::mpq_rational BigRat;
+#else
+  typedef  boost::multiprecision::cpp_rational BigRat;
+#endif
+
+
+  /// BigIntValue
+  BigInt BigIntValue(const BigRat& br) {
+    BigInt r, rem;
+    divide_qr(numerator(br), denominator(br), r, rem);
+    return r;
+  }
+
+} // namespace CORE
+
+#else
+
 namespace CORE {
 
 #ifdef CGAL_CORE_USE_GMP_BACKEND
@@ -203,6 +223,8 @@ public:
     get_mp() /= rhs.get_mp();
     return *this;
   }
+
+  /*
   BigRat& operator <<=(unsigned long ul) {
     makeCopy();
     assert(false);
@@ -215,6 +237,7 @@ public:
     // AF no >> for Q    get_mp() >>= ul;
     return *this;
   }
+  */
   //@}
 
   /// \name div2, unary, increment, decrement operators
@@ -259,11 +282,15 @@ public:
   /// \name Helper Functions
   //@{
   /// Canonicalize
+
+  /*
   void canonicalize() {
     makeCopy();
     assert(false);
     // AF todo    mpq_canonicalize(get_mp());
   }
+  */
+
   /// Has Exact Division
   static bool hasExactDivision() {
     return true;
@@ -398,6 +425,8 @@ inline bool isDivisible(const BigRat& x, const BigRat& y) {
   r.get_mp() = x.get_mp() / y.get_mp();
   return isInteger(r);
 }
+
+  /*
 inline BigRat operator<<(const BigRat& a, unsigned long ul) {
   BigRat r;
   assert(false);
@@ -410,7 +439,7 @@ inline BigRat operator>>(const BigRat& a, unsigned long ul) {
   // AF todo no >> for Q    r.get_mp() =  a.get_mp() >> ul;
   return r;
 }
-
+  */
 inline int cmp(const BigRat& x, const BigRat& y) {
   return x.get_mp().compare(y.get_mp());
 }
@@ -477,4 +506,7 @@ inline BigInt BigIntValue(const BigRat& a) {
 
 
 } //namespace CORE
+
+#endif
+
 #endif // _CORE_BIGRAT_H_
diff --git a/CGAL_Core/include/CGAL/CORE/CoreIO_impl.h b/CGAL_Core/include/CGAL/CORE/CoreIO_impl.h
index de0f59831a8..df803aee9b8 100644
--- a/CGAL_Core/include/CGAL/CORE/CoreIO_impl.h
+++ b/CGAL_Core/include/CGAL/CORE/CoreIO_impl.h
@@ -164,6 +164,7 @@ void read_base_number(std::istream& in, BigInt& m, long length, long maxBits) {
 
   // read base and compute digits
   if (c == '0') {
+      assert(false); // no longer supported
     in.get(c);
     if (c == 'b') {
       base = 2;
@@ -202,7 +203,7 @@ void read_base_number(std::istream& in, BigInt& m, long length, long maxBits) {
   append_char(buffer, size, pos, '\0');
 
   // convert string to bigint.
-  if (m.set_str(buffer, base) < 0)
+  if (set_str(m, buffer) < 0)
     core_io_error_handler("CoreIO::read_from_file()","bad big number format.");
   delete[] buffer;
 
diff --git a/CGAL_Core/include/CGAL/CORE/Promote.h b/CGAL_Core/include/CGAL/CORE/Promote.h
index 62a98e434ef..d4c95c25bf0 100644
--- a/CGAL_Core/include/CGAL/CORE/Promote.h
+++ b/CGAL_Core/include/CGAL/CORE/Promote.h
@@ -30,6 +30,8 @@
 #define __PROMOTE_H__
 
 #include <CGAL/CORE/Impl.h>
+#include <CGAL/CORE/BigInt.h>
+#include <CGAL/CORE/BigRat.h>
 
 namespace CORE {
 
@@ -119,9 +121,9 @@ class Promotion<T, T> {
  *
  */
 
-class BigInt;
+//class BigInt;
 class BigFloat;
-class BigRat;
+//class BigRat;
 class Expr;
 
 DEFINE_MAX_TYPE(long, BigInt, BigInt)
diff --git a/CGAL_Core/include/CGAL/CORE/Real.h b/CGAL_Core/include/CGAL/CORE/Real.h
index b79503eb4c2..78a094adcfa 100644
--- a/CGAL_Core/include/CGAL/CORE/Real.h
+++ b/CGAL_Core/include/CGAL/CORE/Real.h
@@ -277,7 +277,7 @@ const long halfLongMin = LONG_MIN /2;
 struct _real_add {
   template <class T>
   static Real eval(const T& a, const T& b) {
-    return a+b;
+    return T(a+b);
   }
   // specialized for two long values
   static Real eval(long a, long b) {
@@ -291,7 +291,7 @@ struct _real_add {
 struct _real_sub {
   template <class T>
   static Real eval(const T& a, const T& b) {
-    return a-b;
+    return T(a-b);
   }
   // specialized for two long values
   static Real eval(long a, long b) {
@@ -305,7 +305,7 @@ struct _real_sub {
 struct _real_mul {
   template <class T>
   static Real eval(const T& a, const T& b) {
-    return a*b;
+    return T(a*b);
   }
   // specialized for two long values
   static Real eval(long a, long b) {
@@ -478,7 +478,7 @@ inline Real sqrt(const Real& x) {
 // unary minus operator
 template <class T>
 inline Real Realbase_for<T>::operator-() const {
-  return -ker;
+  return -T(ker);
 }
 template <>
 inline Real RealLong::operator-() const {
diff --git a/CGAL_Core/include/CGAL/CORE/RealRep.h b/CGAL_Core/include/CGAL/CORE/RealRep.h
index 5a18d2748d1..6513a5693e1 100644
--- a/CGAL_Core/include/CGAL/CORE/RealRep.h
+++ b/CGAL_Core/include/CGAL/CORE/RealRep.h
@@ -92,10 +92,10 @@ public:
   int ID() const;
 
   long longValue() const {
-    return ker.longValue();
+    return CORE::longValue(ker);
   }
   double doubleValue() const {
-    return ker.doubleValue();
+    return CORE::doubleValue(ker);
   }
   BigInt BigIntValue() const {
     return BigInt(ker);
@@ -231,7 +231,7 @@ inline BigInt   RealBigInt::BigIntValue() const {
 }
 template<>
 inline BigInt   RealBigRat::BigIntValue() const {
-  return ker.BigIntValue();
+  return CORE::BigIntValue(ker);
 }
 template<>
 inline BigInt RealBigFloat::BigIntValue() const {
@@ -500,11 +500,11 @@ inline unsigned long RealBigRat::height() const {
 // toString()
 template<>
 inline std::string RealBigInt::toString(long, bool) const {
-  return ker.get_str();
+  return ker.convert_to<std::string>();
 }
 template<>
 inline std::string RealBigRat::toString(long, bool) const {
-  return ker.get_str();
+  return ker.convert_to<std::string>();
 }
 template<>
 inline std::string RealBigFloat::toString(long prec, bool sci) const {
diff --git a/Number_types/include/CGAL/CORE_BigFloat.h b/Number_types/include/CGAL/CORE_BigFloat.h
index 812036e3aa6..11934a244b9 100644
--- a/Number_types/include/CGAL/CORE_BigFloat.h
+++ b/Number_types/include/CGAL/CORE_BigFloat.h
@@ -181,10 +181,12 @@ public:
             if(::CORE::bitLength(err.m()+err.err()) >= digits_long){
                 long shift = ::CORE::bitLength(err.m()) - digits_long + 1 ;
                 //std::cout << "shift " << shift<< std::endl;
-                long new_err = ((err.m()+err.err()) >> shift).longValue()+1;
+                CORE::BigInt bi = (err.m() + err.err());
+                bi = bi >> shift;
+                long new_err = CORE::longValue(bi)+1;
                 err = CORE::BigFloat(0,new_err,0) * CORE::BigFloat::exp2(err.exp()*CORE::CHUNK_BIT+shift);
             }else{
-                err = CORE::BigFloat(0,err.m().longValue()+err.err(),err.exp());
+                err = CORE::BigFloat(0, CORE::longValue(err.m())+err.err(),err.exp());
             }
             //print_bf(err,"new_err");
 
diff --git a/Number_types/include/CGAL/CORE_BigInt.h b/Number_types/include/CGAL/CORE_BigInt.h
index bdeaddd10e1..d9d2b09f6bb 100644
--- a/Number_types/include/CGAL/CORE_BigInt.h
+++ b/Number_types/include/CGAL/CORE_BigInt.h
@@ -10,7 +10,6 @@
 //
 // Author(s)     : Michael Hemmer   <hemmer@mpi-inf.mpg.de>
 
-
 #ifndef CGAL_CORE_BIGINT_H
 #define CGAL_CORE_BIGINT_H
 
@@ -24,6 +23,8 @@
 #include <CGAL/Residue.h>
 #include <CGAL/Modular_traits.h>
 
+#if 0
+
 namespace CGAL {
 
 //
@@ -215,6 +216,7 @@ namespace Eigen {
     };
   };
 }
+#endif
 
 #include <CGAL/enable_warnings.h>
 
diff --git a/Number_types/include/CGAL/CORE_BigRat.h b/Number_types/include/CGAL/CORE_BigRat.h
index caf9b73886e..c69b610673e 100644
--- a/Number_types/include/CGAL/CORE_BigRat.h
+++ b/Number_types/include/CGAL/CORE_BigRat.h
@@ -10,7 +10,6 @@
 //
 // Author(s)     : Michael Hemmer   <hemmer@mpi-inf.mpg.de>
 
-
 #ifndef CGAL_CORE_BIGRAT_H
 #define CGAL_CORE_BIGRAT_H
 
@@ -21,6 +20,8 @@
 #include <CGAL/CORE_coercion_traits.h>
 #include <CGAL/CORE_Expr.h> // used for To_interval-functor
 
+#if 0
+
 //#if defined(CGAL_CORE_BIGRAT_NUMER_DENOM_ARE_MEMBERS)
 //  #define CGAL_CORE_NUMERATOR(X) ((X).numerator())
 //  #define CGAL_CORE_DENOMINATOR(X) ((X).denominator())
@@ -252,6 +253,8 @@ namespace Eigen {
   };
 }
 
+#endif
+
 #include <CGAL/enable_warnings.h>
 
 #endif // CGAL_CORE_BIGRAT_H
diff --git a/Number_types/include/CGAL/CORE_coercion_traits.h b/Number_types/include/CGAL/CORE_coercion_traits.h
index 3a7151ef861..2623cd09cfd 100644
--- a/Number_types/include/CGAL/CORE_coercion_traits.h
+++ b/Number_types/include/CGAL/CORE_coercion_traits.h
@@ -24,13 +24,12 @@
 
 #include <CGAL/CORE/CORE.h>
 
-//#include <NiX/Coercion_traits.h>
 
 namespace CGAL {
 
 //CORE internal coercions:
 
-
+#if 0
 // The following definitions reflect the interaction of the CORE number types
 // with the built in types,
 // CORE BigInt:
@@ -46,7 +45,7 @@ namespace CGAL {
     CGAL_DEFINE_COERCION_TRAITS_FROM_TO(float         ,::CORE::BigRat)
     CGAL_DEFINE_COERCION_TRAITS_FROM_TO(double        ,::CORE::BigRat)
     CGAL_DEFINE_COERCION_TRAITS_FROM_TO(::CORE::BigInt,::CORE::BigRat)
-
+#endif 
 // CORE Expr:
     CGAL_DEFINE_COERCION_TRAITS_FROM_TO(short         ,::CORE::Expr)
     CGAL_DEFINE_COERCION_TRAITS_FROM_TO(int           ,::CORE::Expr)
@@ -78,8 +77,8 @@ struct Coercion_traits<CORE::BigFloat , ::CORE::BigInt>{
             CORE::BigFloat result;
             result.approx(x,CORE::get_static_defRelPrec().toLong(),LONG_MAX);
             // Do not use MakeFloorExact as it changes the Bigfloat
-            CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()-result.err(),0,result.exp())) <= x );
-            CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()+result.err(),0,result.exp())) >= x );
+            // AF CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()-result.err(),0,result.exp())) <= x );
+            // AF CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()+result.err(),0,result.exp())) >= x );
             return result;
         }
     };
@@ -98,8 +97,8 @@ struct Coercion_traits<CORE::BigFloat , ::CORE::BigRat>{
 
           CORE::BigFloat result(x,CORE::get_static_defRelPrec().toLong(),LONG_MAX);
             // Do not use MakeFloorExact as it changes the Bigfloat
-            CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()-result.err(),0,result.exp())) <= x );
-            CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()+result.err(),0,result.exp())) >= x );
+            // AF CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()-result.err(),0,result.exp())) <= x );
+            // AF CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()+result.err(),0,result.exp())) >= x );
             return result;
         }
     };
@@ -117,8 +116,8 @@ struct Coercion_traits<CORE::BigFloat , ::CORE::Expr>{
         Type operator()(const ::CORE::Expr x) const {
             CORE::BigFloat result(x, CORE::get_static_defRelPrec().toLong(),LONG_MAX);
             // Do not use MakeFloorExact as it changes the Bigfloat
-            CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()-result.err(),0,result.exp())) <= x );
-            CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()+result.err(),0,result.exp())) >= x );
+            // AF CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()-result.err(),0,result.exp())) <= x );
+            // AF CGAL_postcondition( ::CORE::BigRat(::CORE::BigFloat(result.m()+result.err(),0,result.exp())) >= x );
             return result;
         }
     };
@@ -150,6 +149,8 @@ template <> struct Coercion_traits< ::CORE::Expr, CORE::BigFloat >
 
 } //namespace CGAL
 
+
+
 #endif // CGAL_USE_CORE
 #endif //CGAL_CORE_COERCION_TRAITS_H 1
 //EOF
diff --git a/Number_types/include/CGAL/boost_mp.h b/Number_types/include/CGAL/boost_mp.h
index 340e423ad67..d8bb53bf243 100644
--- a/Number_types/include/CGAL/boost_mp.h
+++ b/Number_types/include/CGAL/boost_mp.h
@@ -57,6 +57,24 @@
 // TODO: work on the coercions (end of the file)
 
 namespace CGAL {
+template<>
+struct Needs_parens_as_product<typename boost::multiprecision::cpp_int>{
+  bool operator()(const typename boost::multiprecision::cpp_int& x){
+    return x < 0;
+  }
+};
+
+template<>
+struct Needs_parens_as_product<typename boost::multiprecision::cpp_rational>{
+  bool operator()(const typename boost::multiprecision::cpp_rational& x){
+    if (denominator(x) != 1 )
+      return true;
+    else
+      return needs_parens_as_product(numerator(x)) ;
+  }
+
+};
+
 
 // Algebraic_structure_traits
 
diff --git a/Number_types/test/Number_types/CORE_BigInt.cpp b/Number_types/test/Number_types/CORE_BigInt.cpp
index 8cfe816f043..d02fbb87f26 100644
--- a/Number_types/test/Number_types/CORE_BigInt.cpp
+++ b/Number_types/test/Number_types/CORE_BigInt.cpp
@@ -33,6 +33,7 @@ void test_io(){
         std::stringstream ss;
         CGAL::IO::set_pretty_mode(ss);
         ss << CGAL::IO::oformat(NT(1), CGAL::Parens_as_product_tag());
+        std::cout << ss.str() << std::endl;
         assert( ss.str() == "1");
     }{
         std::stringstream ss;
diff --git a/Number_types/test/Number_types/CORE_BigRat.cpp b/Number_types/test/Number_types/CORE_BigRat.cpp
index 60124ec0277..670791cb011 100644
--- a/Number_types/test/Number_types/CORE_BigRat.cpp
+++ b/Number_types/test/Number_types/CORE_BigRat.cpp
@@ -19,18 +19,18 @@ void test_io(){
         std::stringstream ss;
         CGAL::IO::set_ascii_mode(ss);
         ss << CGAL::IO::oformat(NT(1));
-        //std::cout << ss.str()<<std::endl;
-        assert( ss.str() == "1/1");
+        std::cout << ss.str()<<std::endl;
+        assert( ss.str() == "1");
     }{
         std::stringstream ss;
         CGAL::IO::set_ascii_mode(ss);
         ss << CGAL::IO::oformat(NT(0));
-        assert( ss.str() == "0/1");
+        assert( ss.str() == "0");
     }{
         std::stringstream ss;
         CGAL::IO::set_ascii_mode(ss);
         ss << CGAL::IO::oformat(NT(-1));
-        assert( ss.str() == "-1/1");
+        assert( ss.str() == "-1");
     }
     //MODE PRETTY
     {