Physical Units Library Workshop

Overview

The purpose of that workshop is to create a simple physical units library for C++.

It will support:

• several physical dimensions,
• automatic conversions between different units,
• compile time expressions verification,
• literals to easily work with different dimensions and their various units.

Above features will be provided without any runtime performance overhead.

Example:

static_assert(1000 / 1_s == 1_kHz);
static_assert(1_h == 3600_s);
static_assert(1_km + 1_m == 1001_m);
static_assert(10_km / 5_km == 2);
static_assert(10_km / 2 == 5_km);
static_assert(1_km / 1_s == 1000_mps);
static_assert(2_kmph * 2_h == 4_km);
static_assert(2_km / 2_kmph == 1_h);

How to proceed?

1. While solving workshop tasks please do not modify the code in the ref directory to not hit merge conflicts when moving to the next task.
2. The initial state of the task is always provided in the ref/include directory. If you want to use the reference implementation for the next tasks (instead using the one you wrote) than copy headers from ref/include to include before starting the assignment.
3. Reference unit tests and examples are always in ref/src directory. The target of each task is to make that code compile and pass without any issues.
4. If you want to add additional unit tests than please do so in src/tests.cpp file.

Task

static_assert(10_m / 5_s == 2_mps);
static_assert(1_km / 1_s == 1000_mps);
static_assert(2_kmph * 2_h == 4_km);
static_assert(10_Hz * 10_s == 100);
static_assert(2_km / 2_kmph == 1_h);

1. Add definitions to velocity.h header (at least mps and kmph).

2. Add the following operator overloads to quantity interface

   • rep operator*(quantity, quantity)
   • quantity operator*(quantity, quantity)
   • quantity operator/(quantity, quantity) for different dimensions

3. rep operator*(quantity, quantity) should participate in the overload resolution only if the following are true:

   • same_dim<typename Unit::dimension, dim_invert<typename Unit2::dimension>>

4. quantity operator*(quantity, quantity) should participate in the overload resolution only if the following are true:

   • !same_dim<typename Unit::dimension, dim_invert<typename Unit2::dimension>>
   • treat_as_floating_point<decltype(std::declval<Rep>() * std::declval<Rep2>())> or std::ratio_multiply<typename Unit::ratio, typename Unit2::ratio>::den == 1

5. quantity operator/(quantity, quantity) should participate in the overload resolution only if the following are true:

   • !same_dim<typename Unit::dimension, dim_invert<typename Unit2::dimension>>
   • treat_as_floating_point<decltype(std::declval<Rep>() / std::declval<Rep2>())> or std::ratio_divide<typename Unit::ratio, typename Unit2::ratio>::den == 1