diff --git a/Number_types/include/CGAL/cpp_float.h b/Number_types/include/CGAL/cpp_float.h
index 422f76429bd..c5c73645366 100644
--- a/Number_types/include/CGAL/cpp_float.h
+++ b/Number_types/include/CGAL/cpp_float.h
@@ -353,21 +353,27 @@ public:
 
   std::pair<double,double> to_interval() const
   {
-    assert(false);
-    double zero(0);
-    return std::make_pair(zero,zero);
+      if(exp == 0){
+      return CGAL::to_interval(man);
+    }
+    if(exp > 0){
+      Mantissa as = man << exp;
+      return CGAL::to_interval(as);
+    }
+    Mantissa pow(1);
+    pow <<= -exp;
+    boost::multiprecision::cpp_rational rat(man, pow);
+    return CGAL::to_interval(rat);
   }
 
 
   bool is_zero () const {
-    return man==0 && exp == 0;
+    return CGAL::is_zero(man);
   }
 
 
   bool is_one () const {
-    assert(false);
-    return true;
-    //  return exp==0 && size==1 && data()[0]==1;
+    return *this == cpp_float(1);
   }
 
 
@@ -394,8 +400,7 @@ public:
       struct Is_one
         : public CGAL::cpp98::unary_function< Type, bool > {
           bool operator()( const Type& x ) const {
-            assert(false);
-            return false; // x.is_one();
+            return x.is_one();
           }
         };
 
diff --git a/Number_types/test/Number_types/CMakeLists.txt b/Number_types/test/Number_types/CMakeLists.txt
index 925f10a9efc..0b9acb0368d 100644
--- a/Number_types/test/Number_types/CMakeLists.txt
+++ b/Number_types/test/Number_types/CMakeLists.txt
@@ -13,6 +13,7 @@ include(CGAL_VersionUtils)
 include_directories(BEFORE include)
 
 create_single_source_cgal_program("bench_interval.cpp")
+create_single_source_cgal_program("cpp_float.cpp")
 create_single_source_cgal_program("constant.cpp")
 create_single_source_cgal_program("CORE_BigFloat.cpp")
 create_single_source_cgal_program("CORE_BigInt.cpp")
diff --git a/Number_types/test/Number_types/cpp_float.cpp b/Number_types/test/Number_types/cpp_float.cpp
new file mode 100644
index 00000000000..55fb2155a49
--- /dev/null
+++ b/Number_types/test/Number_types/cpp_float.cpp
@@ -0,0 +1,53 @@
+
+#include <CGAL/cpp_float.h>
+
+int main()
+{
+
+  CGAL::cpp_float m(0);
+  std::cout << m << std::endl;
+
+  CGAL::cpp_float m0(23.0);
+
+  CGAL::cpp_float m1(5.0);
+
+  CGAL::cpp_float m2(5.125);
+
+  CGAL::cpp_float m3(2.5);
+
+  CGAL::cpp_float m4(0.625);
+
+
+  CGAL::cpp_float m5(0.5);
+
+  CGAL::is_positive(m5);
+
+  assert(m4 > m5);
+
+  assert(-m4 < -m5);
+
+
+  assert(-m4 == -m4);
+
+
+  assert(-m4 != -m5);
+
+  assert(-m5 != -m4);
+
+  CGAL::cpp_float m15 = m1 + m5;
+  m15 = m15 - m5;
+  assert(m15 == m1);
+  assert(! (m15 < m1));
+  assert(! (m1 < m15));
+
+  m15 = m15 - m15;
+  std::cout << m15 << std::endl;
+  assert(m15.is_zero());
+
+  m1 *= m5;
+
+  m0 += m4;
+  std::cout << m0 << std::endl;
+
+  return 0;
+}