2009/12/3 Jonathan Chambers` <chamber_j@hotmail.com>:
I'm trying to get the program to compile if the variant takes on the guise of an int (because I've implemented void operator()(int &i) const, but not compile if I make the variant take the guise of a char e.g. boost::variant<int, char> var = 'a'; because I've not implemented the void operator()(char &c) const
Can anyone think of a way of doing this, maybe using SFINAE (Substitution Failure Is Not An Error)
I don't think SFINAE will help here, since you don't have a template. What about just declaring, but not defining, the version with a char parameter? Though since it's a runtime distinction, I'm not convinced this will be possible at compile-time, since it will want to compile the code for all the runtime possibilities. What's wrong with just throwing an exception in the char-parameter function in the visitor? Or, alternatively, why are you using a variant<char, int> if you never want it to be a char?