AMDG On 02/25/2013 04:33 PM, Ryan wrote:
at namespace scope in A.cpp:
const metric::nautical_mile_base_unit::unit_type A::nautical_miles;
I don't have a .cpp. Everything is in the header. I tried doing the const thing after the class but it didn't work. Do I have to have a .cpp for it to work?
Ryan
//The following doesn't work. class A { static const metric::nautical_mile_base_unit::unit_type nautical_miles; static const metric::hour_base_unit::unit_type hours; static const decltype(nautical_miles / hours) nautical_miles_per_hour; }
const metric::nautical_mile_base_unit::unit_type A::nautical_miles; const metric::hour_base_unit::unit_type A::hours; const decltype(nautical_miles / hours) A::nautical_miles_per_hour;
That will cause a different linker error. (multiple definitions instead of undefined symbol) It takes a bit of magic to define these in a header. BOOST_UNITS_STATIC_CONSTANT handles it, but it only works at namespace scope. The only to to define them inside the class and keep it header only, is to turn A into a template. In Christ, Steven Watanabe