From: Martin Dowie Strange, I've been doing it in Ada for 15+ years and it's been of /great/ assistance there!! ;-)
I don't know the exact details of Ada's floats, but knowing Ada's approach in general I'd suspect it probably doesn't allow for surprises like those described below (excerpt from http://hal.archives-ouvertes.fr/hal-00128124/en/): [qoute] [...] there exist a number of myths of what IEEE-compliance really entails from the point of view of programsemantics. We shall discuss the following myths, among others: . "Since C's float (resp. double) type is mapped to IEEE single (resp. double) precision arithmetic, arithmetic operations have a uniquely de- fined meaning across platforms." . "Arithmetic operations are deterministic; that is, if I do z=x+y in two places in the same program and my program never touches x and y in the meantime, then the results should be the same." . A variant: "If x < 1 tests true at one point, then x < 1 stays true later if I never modify x." . "The same program, strictly compliant with the C standard with no "un- defined behaviours", should yield identical results if compiled on the same IEEE-compliant platform by different compliant compilers." [end qoute] The 3rd point is crucial WRT using floats with constrained<>.
/But/ you have that with plain-old-code checks anyway, and this library is really just about allowing people to replace these tiresome and repetitive checks with something "automagic".
Right, but checking a float value like this is simply wrong: float f = 1.5; assert(f == 1.5); Constrained types depend on exact comparison, and this is why they're not compatible with built-in floats.
Given that most of the ranges I'm interested in are real numbers this is a "must have" in my book.
Then an exact floating point type should be used as the underlying type instead of the built-in ones. Something like decimal or fixed-point or I don't know what else, anyway a type for which 1.5. == 1.5 for sure. ;-) I'm not aware of any particular class of this kind, but I suppose there should exist several C++ libraries offering this functionality.
Ok, I'll go and dig deeper. It would be nice to be able to say:
bounded_int<int, 0, 100>::type b;
std::cout << "first = " << b.first() << "\n" << "last = " << b.last() << std::endl;
Then write: std::cout << "first = " << b.constraint().lower_bound() << "\n" << "last = " << b.constraint().upper_bound() << std::endl; Note, that bounded_int<>::type is only a typedef of constrained<>. It doesn't contain first() and last(), because bounds are specific only to within_bounds constraint, while constrained<> supports any constraint. For most of other constraints first() and last() simply doesn't make sense (e.g. is_even). Best regards, Robert