Hi all, At last I've managed to find some time to polish the Constrained Value library (former Constrained Types library) and want to share it to hear any opinions and suggestions. If all goes OK, I'll request a formal review when the library is completed. To remind what this library is about, an excerpt from the motivation section of documentation is attached at the bottom of this message. As for now, the implementation is complete, documentation is almost ready, tests and examples have to be finished. The code and documentation can be downloaded here: http://rk.go.pl/f/constrained_value.zip The documentation is also available online here: http://rk.go.pl/r/constrained_value Any feedback is very welcome! Best regards, Robert Kawulak FROM THE MOTIVATION SECTION OF DOCUMENTATION: The Boost Constrained Value library contains class templates useful for creating constrained objects. The simplest example of a constrained object is hour. The only valid values for an hour within a day are integers from the range [0, 23]. There's no C++ type which exactly matches this set of valid values, so a larger integral type (e.g. int) must be used to represent hours. But this can lead to errors -- for instance, one may accidentally assign an invalid value, say 26, to a variable holding an hour. The Boost Constrained Value library provides a mechanism protecting against such mistakes: bounded_int<int, 0, 23>::type hour; hour = 20; // OK hour = 26; // error -- throws an exception Another feature of the library is the ability to specify what happens in case of assignment of an invalid value. For instance, an exception may be thrown as in the example above, or the value may be adjusted to meet the constraint criterions: wrapping_int<int, 0, 255>::type buffer_index; buffer_index = 257; // OK -- adjusts the value to fit in the range by wrapping it assert(buffer_index == 1); The library doesn't focus only on constrained objects that hold a value belonging to a specified range (i.e., bounded objects). Virtually any constraint can be imposed using appropriate predicate: // constraint policy -- a predicate struct is_even { bool operator () (int i) const { return (i % 2) == 0; } }; // and the usage is as simple as: constrained<int, is_even>::type even_int; even_int = 2; // OK even_int++; // error -- throws an exception