AMDG Larry Evans wrote:
Could you post a test case with the before (only 1 expr with 3 args) and after (i.e. 2 expr templates where proto::expr takes 2 args and proto::detail::expr takes 3 args, where the 3ird is the arity) and then maybe some example in proto which specializes on arity and show how the 2 expr template method wouldn't work?
Of course I could try it and see if I could make it fail, but I was hoping you had a better idea of how to make it ( i.e. the 2 expr method) fail.
template<class Tag, class Args, int arity = Args::arity> struct expr3; template<class Tag, class Args> struct expr3<Tag, Args, 2> { typename Args::arg0 arg0; typename Args::arg1 arg1; }; template<class Tag, class Args> struct expr2 { expr3<Tag, Args> args; }; struct test { int i; }; struct my_args { enum { arity = 2 }; typedef test arg0; typedef test arg1; }; struct my_tag {}; int main() { expr3<my_tag, my_args> x3 = { {1}, {1} }; expr2<my_tag, my_args> x2 = { {1}, {1} }; // error C2078: too many initializers } In Christ, Steven Watanabe