Re: [boost] New library proposal: Autodiff

Matt Pulver wrote:

For example, the following will not compile with pre-17 compilers if `constexpr` is dropped:

template constexpr size_t dimension::depth() { if constexpr (is_dimension<RealType>::value) return 1 + RealType::depth(); else return 1; }

This specific case isn't hard to support either, although whether you would want to invest the effort is up to you. template constexpr size_t dimension::depth() { return dimension::depth_impl( is_dimension<RealType>() ); } template constexpr size_t dimension::depth_impl( true_type ) { return 1 + RealType::depth(); } template constexpr size_t dimension::depth_impl( false_type ) { return 1; }