on Mon Jun 25 2012, John Maddock <boost.regex-AT-virgin.net> wrote:
As a single example of this the gmp_int backend triggers a division by 0 signal when one tries to divide the integer by 0; the tom_int raises a hardward signal with a division by 0; the cpp_int throws a std::runtime_error with a division by 0. I would like to see some means by which I could use any integer backend and know that a std::runtime_error would be thrown by a division by 0.
IMO, you should just avoid division by zero period. As far as C++ itself is concerned, division by 0 is undefined behavior, so any code that wants to handle any numeric type including builtins can't assume anything about division by zero.
True, but.... I have some sympathy for Edwards POV, and we could be more newbie friendly in that area.
My original thought was "don't second guess the backend" - in other words let the backend just do whatever it does for each operation, and not try to manhandle different backends towards the same behavior. However, on reflection, division by zero is relatively cheap to test for compared to a full division anyway, so we could check that particular case (or add an extra template param to the backend I guess).
Not only that, but not everybody is writing platform-independent code, and this goes double for people involved in HPC. A long-running calculation that goes down because of divide-by-zero can be extremely expensive. A nod should be given toward ways of handling these issues. -- Dave Abrahams BoostPro Computing http://www.boostpro.com