on Sat Oct 29 2011, "Peter Dimov" <pdimov-AT-pdimov.com> wrote:
Dave Abrahams wrote:
Here's another reason why the first formulation might not be such a hot idea: it rules out some obvious implementations that really ought to be OK. For example,
template <class InputIterator, class T> InputIterator find(InputIterator i, InputIterator j, T value) { while (i != j && !(*i == value)) ++i; return i; }
Yes, but this formulation doesn't need *i and value to be of the same type or operator== to be an equivalence relation. It just needs operator== to return something bool-ish.
Actually it needs a bit more than that: applying ! to your bool-ish thing needs to be unambiguously &&-able with the result of i != j, which might not itself be bool. These are the kinds of problems that crop up when you start checking constraints on valid expressions. -- Dave Abrahams BoostPro Computing http://www.boostpro.com