# C++ named requirements: TrivialClock

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< cpp‎ | named req

The TrivialClock requirements describe the requirements satisfied by several clocks in the chrono library.

### Requirements

For a type TC:

- The type must meet Clock requirements.
- The types TC::rep, TC::duration, and TC::time_point satisfy the requirements of EqualityComparable, LessThanComparable, DefaultConstructible, CopyConstructible, CopyAssignable, Destructible, and NumericType.
- lvalues of the types TC::rep, TC::duration, and TC::time_point are Swappable.
- The function TC::now() does not throw exceptions.
- The type TC::time_point::clock meets the TrivialClock requirements, recursively.

### Usage

The following types in the standard library satisfy these requirements:

- std::chrono::system_clock
- std::chrono::steady_clock
- std::chrono::high_resolution_clock
- `std::filesystem::file_time_type::clock`
- `std::chrono::file_clock`

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