* If the current policy (a template param) is to throw on domain errors (the default), then the second check in the non-member functions is redundant as any errors will have triggered an exception in the distribution constructor. On the other hand: * If the current policy is to not throw (return NaN on domain errors), then the constructor checks are redundant and the non-member function checks are the required ones.
If it really is a performance bottleneck, then we could add a check on the current exception policy so that those two mutually exclusive options get optimized at compile time.
From a performance point of view, suppose I wanted to have a Policy mechanism that allows me to eliminate *all* error checking machine instructions from a distribution constructor of distribution non member function.
Would it be possible to move the detail::check_scale(d) etc into the Policy class? That way I could provide a different policy that get's eliminated compile time via an implementation like "inline policy::check_scale(d){return;}"
I don't think we could move all the checks inside the policy class as each distribution is more or less different, but we could pass a compile time param to the checking functions to have the same effect. In fact can you file a bug report so I don't forget? Cheers, John.