After trying your sample I have only 2 notes -

Use namespace for your library.

And provide microseconds_d, milliseconds_d, etc as part of the library as well (under the same namespace to avoid possible conflicts) so user can easily use ready-made types to switch from one units to another without thinking and plying with typedefs in "PROGRAM" code.

For extending - I feel like have possibility to configure printer to add units literal would be nice and also switch between number output 12345678.50ms and time output 00:01:23.234

After trying your sample I have only 2 notes -

Use namespace for your library.

And provide microseconds_d, milliseconds_d, etc as part of the library as well (under the same namespace to avoid possible conflicts) so user can easily use ready-made types to switch from one units to another without thinking and plying with typedefs in "PROGRAM" code.

For extending - I feel like have possibility to configure printer to add units literal would be nice and also switch between number output 12345678.50ms and time output 00:01:23.234

EDIT

To make clean compilation

• need to fix warning shown by gcc when compiled with -Werror=shadow
• need to include <memory> to avoid error C2039: 'unique_ptr': is not a member of 'std' in VS2017

I strongly feel that any code to be distributed as library should be compiled at highest warning level since it is impossible to perdict the compilation settings of the customer's project