Le lun 08/03/2004 à 20:08, Eric Niebler a écrit :
Michael Stevens wrote:
The test case is very simple.
#include <boost/numeric/interval.hpp> #include <boost/minmax.hpp>
int main() { boost::numeric::interval<float> a,b,c; c = boost::std_max(a, a); }
gcc (2.95.3 and 3.3.1) is only warning "returning reference to temporary". I am surprised this doesn't show up in more cases. Why gcc thinks it needs a temporary here is beyond me
[...]
The fix is to detect whether the unqualified call to max returns an lvalue or not and define the return type of std_max appropriately. Easy enough.
What strikes me as odd with this overload, though, is that max(a,b) in this case will return something that is not equal to either a or b. That seems counter-intuitive. Is this right?
Yes this is right :-) In interval arithmetic, all the functions are usually defined by canonical set extensions. It is also the case for max. Consequently max(A,B) is the interval {max(a,b); a in A and b in B}. When A and B don't overlap, the result is A or B. But it isn't the case when they overlap. And it isn't as much counter-intuitive as you seem to think. How would you define max(A,B) when you have neither A < B nor A > B (it happens when A and B overlap)? Getting A or B in that case would be counter-intuitive. Regards, Guillaume