[Boost-users] enable_if question

I'm just trying to play with enable_if and learn something. I just mean to replace this template method's code: template< bool > void exchange_code( boost::call_traitsstd::string::param_type new_exchange_code ) { if ( boost::is_arithmeticstd::string::value ) { lock lk(guard_ ); exchange_code<false>( new_exchange_code); } else { exchange_code<false>( new_exchange_code); } } With this: template< bool > typename boost::enable_if_c< boost::is_arithmeticstd::string::value, void >::type exchange_code( boost::call_traitsstd::string::param_type new_exchange_code ) { lock lk(guard_ ); exchange_code<false>( new_exchange_code); } template< bool > typename boost::disable_if_c< boost::is_arithmeticstd::string::value , void >::type exchange_code( boost::call_traitsstd::string::param_type new_exchange_code ) { exchange_code<false>( new_exchange_code); } Forget the relevance of the is_arithmetic bit, I use my own needs_lock thingo. For a start: The compiler correctly identifies that ::type is not a member, but SFINAE does not seem to kick in if I'm reading it correctly. ____________________ c:\source\matt\trading_engine\controller\instrument.hpp(66) : error C2039: 'type' : is not a member of 'boost::enable_if_c' with [ B=false, T=void ] c:\source\matt\trading_engine\controller\instrument.hpp(143) : see reference to class template instantiation 'te::instrument<S>' being compiled ____________________ template< bool > typename boost::disable_if_c< boost::is_arithmeticstd::string::value , void >::type exchange_code( boost::call_traitsstd::string::param_type new_exchange_code ) { exchange_code<false>( new_exchange_code); } Is fine... Flipping the conditions round by changing to is_arithmetic< int > flips the failures around. Same issue with the extra parameter approach: template< bool > void exchange_code( boost::call_traitsstd::string::param_type new_exchange_code, typename boost::enable_if_c< boost::is_arithmetic<int>::value, void

::type* dummy = 0 ) { lock lk(guard_ ); exchange_code<false>( new_exchange_code); }

template< bool > void exchange_code( boost::call_traitsstd::string::param_type new_exchange_code, typename boost::disable_if_c< boost::is_arithmetic<int>::value , void >::type* dummy = 0 ) { exchange_code<false>( new_exchange_code); } Is SFINAE meant to work in this way with member templates with enable_if, vc7.1 and boost 1.31? Something simple is probably escaping me... Any thoughts? Regards, Matt Hurd. _______________ Matt Hurd +61.2.8226.5029 hurdm@sig.com Susquehanna _______________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.