There has been some discussion previously on this list for a ranged type. My personal desire was to have new double types in the ranges [0.0, 1.0) and [0.0, 1.0] among other things. There are several other uses that I can imagine. Feel free to rip this apart or do whatever you want. #include <float.h> #include <assert.h> namespace boost { // a simple range class template<class policy> class range { public: typedef range<policy> self; typedef typename policy::value value; range() : m(min()) { } range(const self& x) : m(x) { } range(const value& x) { m = rangeAssert(x); } static const value min() { return policy::min(); } static const value max() { return policy::max(); } operator value() { return m; } self& operator=(const self& x) { m = x; return *this; } self& operator=(const value& x) { m = rangeAssert(x); return *this; } const value& rangeAssert(const value& x) const { assert(x <= max()); assert(x >= min()); return x; }; private: value m; }; // some range policies struct RangePolicyZeroToOne { typedef double value; static const value min() { return 0.0; }; static const value max() { return 1.0; }; }; struct RangePolicyZeroToBelowOne { typedef double value; static const value min() { return 0.0; }; static const value max() { return 1.0 - DBL_EPSILON; }; }; struct RangePolicyPercent { typedef double value; static const value min() { return 0.0; }; static const value max() { return 100.0; }; }; struct RangePolicyDegrees { typedef double value; static const value min() { return 0.0; }; static const value max() { return 360.0 - DBL_EPSILON; }; }; struct RangePolicyRadians { typedef double value; static const value min() { return 0.0; }; static const value max() { return (2 * PI) - DBL_EPSILON; }; }; template <typename T, T min_T, T max_T> struct StaticRange { typedef T value; static const value min() { return min_T; }; static const value max() { return max_T; }; } // some sample types made with ranges typedef range<RangePolicyZeroToOne> Probability; typedef range<RangePolicyZeroToBelowOne> Distribution; typedef range<RangePolicyPercent> Percent; typedef range<RangePolicyDegrees> Degrees; typedef range<RangePolicyRadians> Radians; typedef range<RangePolicyStatic<int, 0, 11> > Month; typedef range<RangePolicyStatic<int, 0, 364> > DayOfTheYear; typedef range<RangePolicyStatic<int, 0, 6> > DayOfTheWeek; typedef range<RangePolicyStatic<char, 'a', 'z'> > LowerCaseLetter; typedef range<RangePolicyStatic<char, 'A', 'Z'> > UpperCaseLetter; typedef range<RangePolicyStatic<char, '0', '9'> > NumberChar; }; by Christopher Diggins licensed under the Boost software license http://www.cdiggins.com http://www.heron-language.com