C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Range type (Re: Proposal: New types in C++0x) Goto page 1, 2  Next          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Robert Kawulak Guest Posted: Wed Sep 29, 2004 8:54 pm    Post subject: Range type (Re: Proposal: New types in C++0x) Hi all, At first, this post was intended only to be an answer for another post in "Proposal: New types in C++0x" thread at c.l.c++.m, but as it proposes a feature many people could possibly be interested in, I've decided to create a new thread for it in c.s.c++. Quote: Will there ever be something as uniform and simple in C++ as int -3000...2000 year ; and typedef int 1...12 month ; I'd much prefer having an std::range class template in the standard library. I see no advantage in a core language solution for this issue, even though I also would like to see it addressed. That's right. This is one of the features C++ IMO lacks. Of course it's not so hard to make such a template class on one's own, but standarising it and recommending to use it instead of built-in types would decrease the number of errors that happen to many C++ programmers, even to the experienced ones. Furthermore, it would make the code more self-documenting and closer to the modelled problem. Maybe the class template could look like this: /************************************************/ template <typename T, T smallest, T biggest> class bounded { //or limited or ranged SATIC_ASSERT( !(biggest < smallest) ); public: bounded(const T & = T(smallest)) /*throw(out_of_bounds, ...)*/; bounded & operator = (const T &) /*throw(out_of_bounds, ...)*/; operator const T & () const throw(); //maybe operators ++, += etc... }; //class bounded<> /************************************************/ Examples of usage: bounded<int, 0, 15> i; // i == 0 //! bounded<int, 1, 56> j(i); // throws: assignment of 0 bounded<int, 1, 56> j(27); // j == 27 i = 10; // i == 10 j = i; // j == 10 int k = i + j; // k == 20; //! i = k; // throws: assignment of 20 Operator < must be defined for operands of type T, and it must preserve linear order. But because of the STATIC_ASSERT, only built-in types could be used. Possible solutions to this problem are: 1. Remove the STATIC_ASSERT - then constructor will always throw if biggest < smallest (very ugly, I admit), because for any x we have: (smallest <= x <= biggest) == false, 2. Add a static member to bounded class and check the condition during its initialisation and eventually throw (even worse...), 3. Require that operator < is inline function with no side effects and allow calls of such functions in compile-time expressions (not ideal, but my favourite). Is there any proposal to the commettee yet? And if no, is it worth making then? Best regards, Robert Kawulak --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Alberto Barbati Guest Posted: Wed Sep 29, 2004 10:36 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) Robert Kawulak wrote: Quote: Hi all, At first, this post was intended only to be an answer for another post in "Proposal: New types in C++0x" thread at c.l.c++.m, but as it proposes a feature many people could possibly be interested in, I've decided to create a new thread for it in c.s.c++. I had exactly the same thought ;-) Quote: Maybe the class template could look like this: /************************************************/ template <typename T, T smallest, T biggest class bounded { //or limited or ranged SATIC_ASSERT( !(biggest < smallest) ); I like it. Especially the way you can use a UDT for the underlying type. The static assert is not a big problem because you could use some template machinery to impose that restriction only if T is a basic type. I was thinking about a completely different approach: struct least_sized_type; // see below template < boost::intmax_t Min, boost::intmax_t Max, typename ImplType = least_sized_type> class bounded { // ... }; The underlying type is specified last so it can be omitted. If it's omitted, it will be automatically detected using some template machinery. This would be used like this: void foo() { bounded<0, 1000, int> i; // use int bounded<0, 1000, short> s; // use short bounded<0, 1000> s1; // use the least-sized integral type // than can represent both 0 and 1000 } I'm not an MPL expert, but I think the auto-detect feature can easily be accomplished by finding in a suitably ordered typelist like: typedef mpl::list< signed char, unsigned char, short, unsigned short, int, unsigned, long, unsigned long, boost::intmax_t> TypeList; the first type that satisfies a condition built upon boost::integer_traits<T>::const_min and boost::integer_traits<T>::const_max. Notice that by changing the TypeList you can have different detection policies, for example: bounded<0, 1000, least_signed_type> // least-sized *and* signed bounded<0, 1000, least_unsigned_type> // least-sized *and* unsigned The two main drawbacks of this approach are: 1) only basic integral types 2) uintmax_t can never be chosen Point 2) could be mitigated by providing a second template (with a different name) taking uintmax_t Min and Max... not very elegant ;-) Just my thoughts, Alberto --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Bob Hairgrove Guest Posted: Wed Sep 29, 2004 11:06 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) On Wed, 29 Sep 2004 20:54:52 GMT, [email]tigrisek (AT) interia (DOT) pl[/email] ("Robert Kawulak") wrote: Quote: Hi all, At first, this post was intended only to be an answer for another post in "Proposal: New types in C++0x" thread at c.l.c++.m, but as it proposes a feature many people could possibly be interested in, I've decided to create a new thread for it in c.s.c++. Will there ever be something as uniform and simple in C++ as int -3000...2000 year ; and typedef int 1...12 month ; I'd much prefer having an std::range class template in the standard library. I see no advantage in a core language solution for this issue, even though I also would like to see it addressed. That's right. This is one of the features C++ IMO lacks. Of course it's not so hard to make such a template class on one's own, but standarising it and recommending to use it instead of built-in types would decrease the number of errors that happen to many C++ programmers, even to the experienced ones. Furthermore, it would make the code more self-documenting and closer to the modelled problem. Maybe the class template could look like this: /************************************************/ template <typename T, T smallest, T biggest class bounded { //or limited or ranged SATIC_ASSERT( !(biggest < smallest) ); public: bounded(const T & = T(smallest)) /*throw(out_of_bounds, ...)*/; bounded & operator = (const T &) /*throw(out_of_bounds, ...)*/; operator const T & () const throw(); //maybe operators ++, += etc... }; //class bounded /************************************************/ Examples of usage: bounded //! bounded<int, 1, 56> j(i); // throws: assignment of 0 bounded<int, 1, 56> j(27); // j == 27 i = 10; // i == 10 j = i; // j == 10 int k = i + j; // k == 20; //! i = k; // throws: assignment of 20 Operator < must be defined for operands of type T, and it must preserve linear order. But because of the STATIC_ASSERT, only built-in types could be used. Possible solutions to this problem are: 1. Remove the STATIC_ASSERT - then constructor will always throw if biggest < smallest (very ugly, I admit), because for any x we have: (smallest <= x <= biggest) == false, 2. Add a static member to bounded class and check the condition during its initialisation and eventually throw (even worse...), 3. Require that operator < is inline function with no side effects and allow calls of such functions in compile-time expressions (not ideal, but my favourite). Is there any proposal to the commettee yet? And if no, is it worth making then? There is a Boost interval library as well as a graph programming library, the latter of these having objects such as directed graphs/edges. Have you seen these? I think the concept of the assertion !(biggest < smallest) is not always desirable if one wishes to implement a directed range. I did my own template class for some scheduling work, but it has additional features similar to set operations (such as intersection, complement, coalesce unions) which aren't generally applicable to other problem domains. I think it's very hard to cover all the bases. -- Bob Hairgrove [email]NoSpamPlease (AT) Home (DOT) com[/email] --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Alberto Barbati Guest Posted: Thu Sep 30, 2004 12:26 am    Post subject: Re: Range type (Re: Proposal: New types in C++0x) Bob Hairgrove wrote: Quote: There is a Boost interval library as well as a graph programming library, the latter of these having objects such as directed graphs/edges. Have you seen these? I think the concept of the assertion !(biggest < smallest) is not always desirable if one wishes to implement a directed range. I did my own template class for some scheduling work, but it has additional features similar to set operations (such as intersection, complement, coalesce unions) which aren't generally applicable to other problem domains. I think it's very hard to cover all the bases. I think you're missing the point. The Boost interval library is about a *objects* that represents ranges of values. On such objects it makes sense to do set-theoretic operations like intersection, etc. Here we are discussing about *types* that represents a range of values. Objects of any such type would represent only one value in the allotted range. That is if x is of type bounded<0, 100>, then x can take any *one* value like 0, 1, 2, 33 or 100. Set-theoretic operations makes no sense on x, but arithmetic operations do: for example you can increment x, possibly throwing an exception on overflow if x is already 100. In this case there's no point in having directed ranges, therefore the idea of having the !(smallest > biggest) test as a diagnostic for empty ranges also makes sense. Alberto --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Nicolas Pavlidis Guest Posted: Thu Sep 30, 2004 5:13 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) [email]tigrisek (AT) interia (DOT) pl[/email] ("Robert Kawulak") writes: Quote: /************************************************/ template <typename T, T smallest, T biggest I wrote such a class and the header of the template was nearly the same but still there was a little difference: template T smallest = std::numeric_limits T biggest = std::numeric_limits<T>::max> Quote: Operator < must be defined for operands of type T, and it must preserve linear order. But because of the STATIC_ASSERT, only built-in types could be I don't think that tis is a problem, because ranges make only sense for build in types. But if you wish support for non build in types it's IMHO better to use the assert - macro in the constructor instade of an exception. Kind regards, Nicolas -- Quote: Nicolas Pavlidis | Elvis Presly: | |__ | Student of SE & KM | "Into the goto" | |__| | [email]pavnic (AT) sbox (DOT) tugraz.at[/email] | ICQ #320057056 | | -------------------University of Technology, Graz----------------| --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Nicolas Pavlidis Guest Posted: Fri Oct 01, 2004 4:59 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) [email]pavnic (AT) sbox (DOT) tugraz.at[/email] (Nicolas Pavlidis) writes: Quote: tigrisek (AT) interia (DOT) pl ("Robert Kawulak") writes: /************************************************/ template <typename T, T smallest, T biggest I wrote such a class and the header of the template was nearly the same but still there was a little difference: template T smallest = std::numeric_limits T biggest = std::numeric_limits<T>::max This is bulshit, sorry. I don't know what I've done, because I did't find the file anymore, but there was certainly no call to std::numeric_limits<t>::min / max, because these are functions . I'm sorry for my wrong code. Kind regards, Nicolas -- Quote: Nicolas Pavlidis | Elvis Presly: | |__ | Student of SE & KM | "Into the goto" | |__| | [email]pavnic (AT) sbox (DOT) tugraz.at[/email] | ICQ #320057056 | | -------------------University of Technology, Graz----------------| --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Nicola Musatti Guest Posted: Sat Oct 02, 2004 4:55 am    Post subject: Re: Range type (Re: Proposal: New types in C++0x) [email]AlbertoBarbati (AT) libero (DOT) it[/email] (Alberto Barbati) wrote in message news:<FHG6d.15202$H11.463970 (AT) twister1 (DOT) libero.it>... [...] Quote: struct least_sized_type; // see below template boost::intmax_t Min, boost::intmax_t Max, typename ImplType = least_sized_type class bounded { // ... }; The underlying type is specified last so it can be omitted. If it's omitted, it will be automatically detected using some template machinery. I posted a very similar idea on c.l.c++.m a few moments ago, so I obviously favour your solution. [...] Quote: I'm not an MPL expert, but I think the auto-detect feature can easily be accomplished by finding in a suitably ordered typelist [...] the first type that satisfies a condition built upon boost::integer_traits<T>::const_min and boost::integer_traits<T>::const_max. Notice that by changing the TypeList you can have different detection policies, for example: bounded<0, 1000, least_signed_type> // least-sized *and* signed bounded<0, 1000, least_unsigned_type> // least-sized *and* unsigned The two main drawbacks of this approach are: 1) only basic integral types 2) uintmax_t can never be chosen Point 2) could be mitigated by providing a second template (with a different name) taking uintmax_t Min and Max... not very elegant Why? We could have integral_bounded and unsigned_bounded. Once exact floating point constants make it into the language it will be reasonable to extend non type template parameters to floating point types and we'll be able to add floating_unbounded. Cheers, Nicola Musatti --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Xenos Guest Posted: Sat Oct 02, 2004 4:55 am    Post subject: Re: Range type (Re: Proposal: New types in C++0x) "Nicolas Pavlidis" <pavnic (AT) sbox (DOT) tugraz.at> wrote Quote: tigrisek (AT) interia (DOT) pl ("Robert Kawulak") writes: template<typenane T, T smallest = std::numeric_limits T biggest = std::numeric_limits<T>::max I usually do this: class default_type{}; template<typename T, T lo, T hi, typename U = default_type> so I can recreate "unique" types, so that if I have two different types with the same T and range, the compiler will still see them as different types if I prefer. Quote: I don't think that tis is a problem, because ranges make only sense for build in types. But if you wish support for non build in types it's IMHO better to use the assert - macro in the constructor instade of an exception. Except (no pun intended) in a fault tolerent system that must recover from the bounds error an not abort or ignore it. You can say that you should have caught it in testing, but realistically bugs will still exist in validated production code that must not terminate because of an error. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Robert Kawulak Guest Posted: Sat Oct 02, 2004 4:55 am    Post subject: Re: Range type (Re: Proposal: New types in C++0x) Hi, Quote: template<typenane T, T smallest = std::numeric_limits T biggest = std::numeric_limits<T>::max Nice! ;-) Quote: ranges make only sense for build in types. I must disagree here. Range makes sense for any type for which a linear order relation is defined (for example an infinite precision numbers class). Quote: But if you wish support for non build in types it's IMHO better to use the assert - macro in the constructor instade of an exception. Unfortunately I've missed one thing - because of 'smallest' and 'biggest' template parameters of type T, the T can only be an integral type (I must had been really sleepy when writing the post at night to forget about this . It's a pity, because one can't use any user-defined type or even std::bounded<double, 0.0, 1.0>. But at least this solves the problem of STATIC_CAST... We can try to use some template metaprogramming to create a class for those cases, but is it possible to make and does somebody know how to make it? Thanks for your reply! Best regards, Robert Kawulak --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Alberto Barbati Guest Posted: Sat Oct 02, 2004 4:27 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) Nicola Musatti wrote: Quote: AlbertoBarbati (AT) libero (DOT) it (Alberto Barbati) wrote in message news:<FHG6d.15202$H11.463970 (AT) twister1 (DOT) libero.it>... I posted a very similar idea on c.l.c++.m a few moments ago, so I obviously favour your solution. :-) I also wrote a sample implementation, but I still don't see yours in the newsgroup. If you want to, feel free to send me yours privately. Can I send you mine? Quote: The two main drawbacks of this approach are: 1) only basic integral types In fact I realized that this is not a drawback... Only basic integral types can be used in non-type template parameters. So no UDTs and no floating point (yet) can ever be used. Allowing UDTs would require the use of pointers to values as the template parameters, so it may still be done, but the syntax would become quite cumbersome. Quote: 2) uintmax_t can never be chosen Point 2) could be mitigated by providing a second template (with a different name) taking uintmax_t Min and Max... not very elegant ;-) Why? We could have integral_bounded and unsigned_bounded. Maybe it's not that bad, after all. But as you can write (at least you can with my implementation): integral_bounded<0, 1000, least_unsigned> why should I bother using: unsigned_bounded<0, 1000> ? Moreover what should we do in this case: unsigned_bounded<0, 1000, least_signed> ? I don't feel like disallowing it, yet it is counter-intuitive to have a type named unsigned_bounded be... signed. In a certain sense, unsigned_bounded is only needed if your range really won't fit in a intmax_t, a very limited use, so we might decide to dump it altogether. Quote: Why? We could have integral_bounded and unsigned_bounded. Once exact floating point constants make it into the language it will be reasonable to extend non type template parameters to floating point types and we'll be able to add floating_unbounded. Yep :-P Ciao, Alberto --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Nicolas Pavlidis Guest Posted: Sat Oct 02, 2004 4:27 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) [email]dont.spam.me (AT) pool (DOT) domainsite.com[/email] (Xenos) writes: Quote: "Nicolas Pavlidis" <pavnic (AT) sbox (DOT) tugraz.at> wrote in message news:2s21uvF1f1b5vU1 (AT) uni-berlin (DOT) de... I don't think that tis is a problem, because ranges make only sense for build in types. But if you wish support for non build in types it's IMHO better to use the assert - macro in the constructor instade of an exception. Except (no pun intended) in a fault tolerent system that must recover from the bounds error an not abort or ignore it. You can say that you should have caught it in testing, but realistically bugs will still exist in validated production code that must not terminate because of an error. But the upper and the lower bouds are given at compile time, so if there are wrong number passed it's definitely a wrong ese of the class, IMHO Kind regrads, Nicolas -- Quote: Nicolas Pavlidis | Elvis Presly: | |__ | Student of SE & KM | "Into the goto" | |__| | [email]pavnic (AT) sbox (DOT) tugraz.at[/email] | ICQ #320057056 | | -------------------University of Technology, Graz----------------| --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Terje Slettebø Guest Posted: Sun Oct 03, 2004 2:50 am    Post subject: Re: Range type (Re: Proposal: New types in C++0x) "Nicolas Pavlidis" <pavnic (AT) sbox (DOT) tugraz.at> wrote Quote: pavnic (AT) sbox (DOT) tugraz.at (Nicolas Pavlidis) writes: [email]tigrisek (AT) interia (DOT) pl[/email] ("Robert Kawulak") writes: /************************************************/ template <typename T, T smallest, T biggest I wrote such a class and the header of the template was nearly the same but still there was a little difference: template T smallest = std::numeric_limits T biggest = std::numeric_limits<T>::max This is bulshit, sorry. I don't know what I've done, because I did't find the file anymore, but there was certainly no call to std::numeric_limits<t>::min / max, because these are functions . Try boost/integer_traits.hpp ([url]http://www.boost.org/libs/integer/integer_traits.html)[/url], which addresses just this problem: template<typenane T, T smallest = boost::integer_traits T biggest = boost::integer_traits<T>::const_max> ... Regards, Terje --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Nicola Musatti Guest Posted: Mon Oct 04, 2004 3:16 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) [email]AlbertoBarbati (AT) libero (DOT) it[/email] (Alberto Barbati) wrote in message news:<OIv7d.20029$N45.508594 (AT) twister2 (DOT) libero.it>... Quote: Nicola Musatti wrote: [...] I also wrote a sample implementation, but I still don't see yours in the newsgroup. If you want to, feel free to send me yours privately. Can I send you mine? Oh, I don't have a complete implementation. Mine was only a very rough proof of concept. [...] Quote: Why? We could have integral_bounded and unsigned_bounded. Maybe it's not that bad, after all. But as you can write (at least you can with my implementation): integral_bounded<0, 1000, least_unsigned why should I bother using: unsigned_bounded<0, 1000> ? Moreover what should we do in this case: unsigned_bounded<0, 1000, least_signed> ? I don't feel like disallowing it, yet it is counter-intuitive to have a type named unsigned_bounded be... signed. In a certain sense, unsigned_bounded is only needed if your range really won't fit in a intmax_t, a very limited use, so we might decide to dump it altogether. Hold it. unsigned_bounded is quite a different beast from integer_bounded in that it should support modulo arithmetic! We (I, at least) tend to consider unsigned as an integer subset, but it really is a different type, with different semantics. So integer_bounded and unsigned_bounded shouldn't share the set of valid base types. Another issue to consider is whether a signed range should simply be represented by the smallest type that can represent both extremes or if the extremes should be traslated to an interval symmetric around zero, so as to use the smallest base type possible, at the expense of inverting the traslation on most operations. Cheers, Nicola Musatti --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Robert Kawulak Guest Posted: Mon Oct 04, 2004 6:24 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) Hi, I see that some people here have already written such a class template. All the authors - maybe you could post your work here, so we can compare and contrast features and different approaches you've used, and choose the best solutions? For a start, here's improved interface of the class template from the opening post: /**************************************************************/ template <typename T, T S, T B> class bounded { public: // Remember the template's actual parameters typedef T value_type; static const T smallest = S; static const T biggest = B; // Constructor (also default) bounded(value_type = smallest) throw(std::range_error); // Assignment operator bounded & operator = (value_type) throw(std::range_error); // No need to define copy constructor nor destructor // Operator for conversion to value_type operator value_type () const throw(); // Other mutating operators value_type operator ++ () throw(std::range_error); value_type operator -- () throw(std::range_errornds); value_type operator ++ (int) throw(std::range_error); value_type operator -- (int) throw(std::range_error); value_type operator += (value_type) throw(std::range_error); value_type operator -= (value_type) throw(std::range_error); value_type operator *= (value_type) throw(std::range_error); value_type operator /= (value_type) throw(std::range_error); value_type operator %= (value_type) throw(std::range_error); private: // To prevent instantiation with incorrect parameters: SATIC_ASSERT( smallest <= biggest ); }; //class bounded<> /**************************************************************/ Here are also some reflections of mine: 1. Name of the class template: so far, these seem reasonable to me: bounded ranged limited 2. I think that trying to instantiate the template with invalid range should cause a compile-time error. STATIC_ASSERT is not in the standard yet, but there are several proposals concerning it. Even if it is not added to the language, it can be easily replaced with template metaassertion with no side effects (like namespace pollution - it may be whole contained in the private section of the class template). 3. There are two possible approaches for implementing mutating operators like ++, --, +=, *=, etc.: ignore possible overflow and throw only when the (possibly wrapped) result doesn't fit in the range or check whether the operation would cause overflow and throw if yes. I'd choose the latter, because for signed types overflow entails undefined behavior and because ignoring the overflow might hide bugs and errors. 4. I also wonder if the following operators should be included: ^=, &=, |=, Quote: =, <<=. 5. Should there be a separate excepion class or std::range_error is OK? Best regards, Robert Kawulak --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Alberto Barbati Guest Posted: Tue Oct 05, 2004 3:27 pm    Post subject: Re: Range type (Re: Proposal: New types in C++0x) Robert Kawulak wrote: Quote: Hi, I see that some people here have already written such a class template. All the authors - maybe you could post your work here, so we can compare and contrast features and different approaches you've used, and choose the best solutions? After finished writing my (long) post I realized that this may be not the right newsgroup for that. Why don't we move to Boost instead? Just my opinion, Alberto --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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