on Fri Nov 02 2012, Brian Simpson <wheber-AT-hotmail.com> wrote:
Dave Abrahams <dave <at> boostpro.com> writes:
<snip>
- Do the semantics for are_strict_equals at http://www.boost.org/doc/libs/1_51_0/doc/html/variant/tutorial.html differ from those of the built-in equality operator?
The built-in equality operator compares two instances of identically-typed variant. As a binary visitor, however, are_strict_equals can compare non-identically-typed variants.
Interesting. hard to think of that as "strict," though.
boost::variant<int, std::string> v1("hello"); boost::variant<int, std::string> v2("g'bye"); boost::variant<double, std::string> v3("hello"); assert(!(v1 == v2)); assert(v1 == v3);//compile error assert(boost::apply_visitor(are_strict_equals(), v1, v3));
Interestingly, it looks as if variant goes the extra mile to "prevent comparison with foreign types" (that's a comment from variant.hpp). I wonder why.
Yeah. FWIW, while I do appreciate the answers, my *main* intention in posting these comments was to get the maintainer to fix the documentation. Hint, hint :-) -- Dave Abrahams BoostPro Computing Software Development Training http://www.boostpro.com Clang/LLVM/EDG Compilers C++ Boost