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[SVN r8702]

include/boost/detail/numeric_traits.hpp

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+// (C) Copyright David Abrahams 2001. Permission to copy, use, modify,
+// sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+//
+// Template class is_signed and its documentation is:
+// (C) Copyright Howard Hinnant 2001. Permission to copy, use, modify,
+// sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+//
+// Template class numeric_traits<Number> --
+//
+//    Supplies:
+//
+//      typedef difference_type -- a type used to represent the difference
+//      between any two values of Number.
+//
+//    Support:
+//      1. Not all specializations are supplied
+//
+//      2. Use of specializations that are not supplied will cause a
+//      compile-time error
+//
+//      3. Users are free to specialize numeric_traits for any type.
+//
+//      4. Right now, specializations are only supplied for integer types.
+//
+//      5. On implementations which do not supply compile-time constants in
+//      std::numeric_limits<>, only specializations for built-in integer types
+//      are supplied.
+//
+//      6. Handling of numbers whose range of representation is at least as
+//      great as boost::intmax_t can cause some differences to be
+//      unrepresentable in difference_type:
+//
+//        Number    difference_type
+//        ------    ---------------
+//        signed    Number
+//        unsigned  intmax_t
+//
+// template <class Number> typename numeric_traits<Number>::difference_type
+// numeric_distance(Number x, Number y)
+//    computes (y - x), attempting to avoid overflows.
+//
+
+// See http://www.boost.org for most recent version including documentation.
+
+// Revision History
+// 21 Jan 2001 - Created
+
+#ifndef BOOST_NUMERIC_TRAITS_HPP_DWA20001901
+# define BOOST_NUMERIC_TRAITS_HPP_DWA20001901
+
+# include <boost/config.hpp>
+# include <boost/cstdint.hpp>
+# include <boost/static_assert.hpp>
+# include <boost/type_traits.hpp>
+# ifndef BOOST_NO_LIMITS
+#  include <limits>
+# endif
+
+namespace boost { namespace detail {
+
+  // Template class if_true -- select among 2 types based on a bool constant expression
+  // Usage:
+  //   typename if_true<(bool_const_expression)>::template then<true_type, false_type>::type
+  template <bool> struct if_true;
+
+  template <>
+  struct if_true<true>
+  {
+      template <class T1, class T2>
+      struct then { typedef T1 type; };
+  };
+
+  template <>
+  struct if_true<false>
+  {
+      template <class T1, class T2>
+      struct then { typedef T2 type; };
+  };
+
+  // Template class is_signed -- determine whether a numeric type is signed
+  // Requires that T is constructable from the literals -1 and 0.  Compile-time
+  // error results if that requirement is not met (and thus signedness is not
+  // likely to have meaning for that type).
+  template <class Number>
+  struct is_signed
+  {
+      enum { value = (Number(-1) < Number(0)) };
+  };
+
+  // Template class integer_traits<Integer> -- traits of various integer types
+  // This should probably be rolled into boost::integer_traits one day, but I
+// need it to work without <limits>
+  template <class Integer>
+  struct integer_traits
+  {
+# ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
+   private:
+      typedef Integer integer_type;
+      typedef std::numeric_limits<integer_type> x;
+#   ifdef BOOST_MSVC
+      enum { is_integer = x::is_integer };
+#   endif
+   public:
+#  ifndef BOOST_MSVC // for some reason, this asserts when it shouldn't
+      BOOST_STATIC_ASSERT(x::is_integer);
+#  else
+      BOOST_STATIC_ASSERT(is_integer);
+#  endif
+      typedef typename
+      if_true<x::is_signed
+              & !(x::is_bounded
+                  | x::digits >= std::numeric_limits<boost::intmax_t>::digits)>::template then<
+        Integer,
+          
+      typename if_true<(x::digits < std::numeric_limits<signed int>::digits)>::template then<
+        signed int,
+
+      typename if_true<(x::digits < std::numeric_limits<signed long>::digits)>::template then<
+        signed long,
+
+   // else
+        intmax_t
+      >::type>::type>::type difference_type;
+# else
+      BOOST_STATIC_ASSERT(boost::is_integral<Integer>::value);
+      
+      typedef typename
+      if_true<(sizeof(Integer) >= sizeof(intmax_t))>::template then<
+               
+        typename if_true<is_signed<Integer>::value>::template then<
+          Integer,
+          intmax_t
+        >::type,
+
+        typename if_true<(sizeof(Integer) < sizeof(std::ptrdiff_t))>::template then<
+          std::ptrdiff_t,
+          intmax_t
+        >::type
+      >::type difference_type;
+# endif
+  };
+
+  // Right now, only supports integers, but should be expanded.
+  template <class Number>
+  struct numeric_traits
+  {
+      typedef typename integer_traits<Number>::difference_type difference_type;
+  };
+
+  template <class Number>
+  typename numeric_traits<Number>::difference_type numeric_distance(Number x, Number y)
+  {
+      typedef typename numeric_traits<Number>::difference_type difference_type;
+      return difference_type(y) - difference_type(x);
+  }
+}}
+
+#endif // BOOST_NUMERIC_TRAITS_HPP_DWA20001901