sl@0: // (C) Copyright David Abrahams 2001, Howard Hinnant 2001.
sl@0: //
sl@0: // Distributed under the Boost Software License, Version 1.0. (See
sl@0: // accompanying file LICENSE_1_0.txt or copy at
sl@0: // http://www.boost.org/LICENSE_1_0.txt)
sl@0: //
sl@0: // Template class numeric_traits<Number> --
sl@0: //
sl@0: //    Supplies:
sl@0: //
sl@0: //      typedef difference_type -- a type used to represent the difference
sl@0: //      between any two values of Number.
sl@0: //
sl@0: //    Support:
sl@0: //      1. Not all specializations are supplied
sl@0: //
sl@0: //      2. Use of specializations that are not supplied will cause a
sl@0: //      compile-time error
sl@0: //
sl@0: //      3. Users are free to specialize numeric_traits for any type.
sl@0: //
sl@0: //      4. Right now, specializations are only supplied for integer types.
sl@0: //
sl@0: //      5. On implementations which do not supply compile-time constants in
sl@0: //      std::numeric_limits<>, only specializations for built-in integer types
sl@0: //      are supplied.
sl@0: //
sl@0: //      6. Handling of numbers whose range of representation is at least as
sl@0: //      great as boost::intmax_t can cause some differences to be
sl@0: //      unrepresentable in difference_type:
sl@0: //
sl@0: //        Number    difference_type
sl@0: //        ------    ---------------
sl@0: //        signed    Number
sl@0: //        unsigned  intmax_t
sl@0: //
sl@0: // template <class Number> typename numeric_traits<Number>::difference_type
sl@0: // numeric_distance(Number x, Number y)
sl@0: //    computes (y - x), attempting to avoid overflows.
sl@0: //
sl@0: 
sl@0: // See http://www.boost.org for most recent version including documentation.
sl@0: 
sl@0: // Revision History
sl@0: // 11 Feb 2001 - Use BOOST_STATIC_CONSTANT (David Abrahams)
sl@0: // 11 Feb 2001 - Rolled back ineffective Borland-specific code
sl@0: //               (David Abrahams)
sl@0: // 10 Feb 2001 - Rolled in supposed Borland fixes from John Maddock, but
sl@0: //               not seeing any improvement yet (David Abrahams)
sl@0: // 06 Feb 2001 - Factored if_true out into boost/detail/select_type.hpp
sl@0: //               (David Abrahams)
sl@0: // 23 Jan 2001 - Fixed logic of difference_type selection, which was
sl@0: //               completely wack. In the process, added digit_traits<>
sl@0: //               to compute the number of digits in intmax_t even when
sl@0: //               not supplied by numeric_limits<>. (David Abrahams)
sl@0: // 21 Jan 2001 - Created (David Abrahams)
sl@0: 
sl@0: #ifndef BOOST_NUMERIC_TRAITS_HPP_DWA20001901
sl@0: # define BOOST_NUMERIC_TRAITS_HPP_DWA20001901
sl@0: 
sl@0: # include <boost/config.hpp>
sl@0: # include <boost/cstdint.hpp>
sl@0: # include <boost/static_assert.hpp>
sl@0: # include <boost/type_traits.hpp>
sl@0: # include <boost/detail/select_type.hpp>
sl@0: # include <boost/limits.hpp>
sl@0: 
sl@0: namespace boost { namespace detail {
sl@0: 
sl@0:   // Template class is_signed -- determine whether a numeric type is signed
sl@0:   // Requires that T is constructable from the literals -1 and 0.  Compile-time
sl@0:   // error results if that requirement is not met (and thus signedness is not
sl@0:   // likely to have meaning for that type).
sl@0:   template <class Number>
sl@0:   struct is_signed
sl@0:   {
sl@0: #if defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) || defined(BOOST_MSVC) && BOOST_MSVC <= 1300
sl@0:     BOOST_STATIC_CONSTANT(bool, value = (Number(-1) < Number(0)));
sl@0: #else
sl@0:     BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<Number>::is_signed);
sl@0: #endif
sl@0:   };
sl@0: 
sl@0: # ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
sl@0:   // digit_traits - compute the number of digits in a built-in integer
sl@0:   // type. Needed for implementations on which numeric_limits is not specialized
sl@0:   // for intmax_t (e.g. VC6).
sl@0:   template <bool is_specialized> struct digit_traits_select;
sl@0: 
sl@0:   // numeric_limits is specialized; just select that version of digits
sl@0:   template <> struct digit_traits_select<true>
sl@0:   {
sl@0:       template <class T> struct traits
sl@0:       {
sl@0:           BOOST_STATIC_CONSTANT(int, digits = std::numeric_limits<T>::digits);
sl@0:       };
sl@0:   };
sl@0: 
sl@0:   // numeric_limits is not specialized; compute digits from sizeof(T)
sl@0:   template <> struct digit_traits_select<false>
sl@0:   {
sl@0:       template <class T> struct traits
sl@0:       {
sl@0:           BOOST_STATIC_CONSTANT(int, digits = (
sl@0:               sizeof(T) * std::numeric_limits<unsigned char>::digits
sl@0:               - (is_signed<T>::value ? 1 : 0))
sl@0:               );
sl@0:       };
sl@0:   };
sl@0: 
sl@0:   // here's the "usable" template
sl@0:   template <class T> struct digit_traits
sl@0:   {
sl@0:       typedef digit_traits_select<
sl@0:                 ::std::numeric_limits<T>::is_specialized> selector;
sl@0:       typedef typename selector::template traits<T> traits;
sl@0:       BOOST_STATIC_CONSTANT(int, digits = traits::digits);
sl@0:   };
sl@0: #endif
sl@0: 
sl@0:   // Template class integer_traits<Integer> -- traits of various integer types
sl@0:   // This should probably be rolled into boost::integer_traits one day, but I
sl@0:   // need it to work without <limits>
sl@0:   template <class Integer>
sl@0:   struct integer_traits
sl@0:   {
sl@0: # ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
sl@0:    private:
sl@0:       typedef Integer integer_type;
sl@0:       typedef std::numeric_limits<integer_type> x;
sl@0: #   if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
sl@0:       // for some reason, MSVC asserts when it shouldn't unless we make these
sl@0:       // local definitions
sl@0:       BOOST_STATIC_CONSTANT(bool, is_integer = x::is_integer);
sl@0:       BOOST_STATIC_CONSTANT(bool, is_specialized = x::is_specialized);
sl@0:       
sl@0:       BOOST_STATIC_ASSERT(is_integer);
sl@0:       BOOST_STATIC_ASSERT(is_specialized);
sl@0: #   endif
sl@0:    public:
sl@0:       typedef typename
sl@0:       if_true<(int(x::is_signed)
sl@0:               && (!int(x::is_bounded)
sl@0:                  // digits is the number of no-sign bits
sl@0:                   || (int(x::digits) + 1 >= digit_traits<boost::intmax_t>::digits)))>::template then<
sl@0:         Integer,
sl@0:           
sl@0:       typename if_true<(int(x::digits) + 1 < digit_traits<signed int>::digits)>::template then<
sl@0:         signed int,
sl@0: 
sl@0:       typename if_true<(int(x::digits) + 1 < digit_traits<signed long>::digits)>::template then<
sl@0:         signed long,
sl@0: 
sl@0:    // else
sl@0:         intmax_t
sl@0:       >::type>::type>::type difference_type;
sl@0: #else
sl@0:       BOOST_STATIC_ASSERT(boost::is_integral<Integer>::value);
sl@0: 
sl@0:       typedef typename
sl@0:       if_true<(sizeof(Integer) >= sizeof(intmax_t))>::template then<
sl@0:                
sl@0:         typename if_true<(is_signed<Integer>::value)>::template then<
sl@0:           Integer,
sl@0:           intmax_t
sl@0:         >::type,
sl@0: 
sl@0:         typename if_true<(sizeof(Integer) < sizeof(std::ptrdiff_t))>::template then<
sl@0:           std::ptrdiff_t,
sl@0:           intmax_t
sl@0:         >::type
sl@0:       >::type difference_type;
sl@0: # endif
sl@0:   };
sl@0: 
sl@0:   // Right now, only supports integers, but should be expanded.
sl@0:   template <class Number>
sl@0:   struct numeric_traits
sl@0:   {
sl@0:       typedef typename integer_traits<Number>::difference_type difference_type;
sl@0:   };
sl@0: 
sl@0:   template <class Number>
sl@0:   typename numeric_traits<Number>::difference_type numeric_distance(Number x, Number y)
sl@0:   {
sl@0:       typedef typename numeric_traits<Number>::difference_type difference_type;
sl@0:       return difference_type(y) - difference_type(x);
sl@0:   }
sl@0: }}
sl@0: 
sl@0: #endif // BOOST_NUMERIC_TRAITS_HPP_DWA20001901