This is a traits class to identify which types of count representations (as those used internally by duration) act as floating-point types, and thus allow for fractional counts.
The standard only provides the default definition, which is the same as the is_floating_point trait for the type, but a specific type of count representation can specialize this template to be either a true_type or a false_type.
Template parameters
Rep
Count representation type.
This is an arithmetic type, or a class emulating an arithmetic type.