forked from mpusz/mp-units
72 lines
2.7 KiB
ReStructuredText
72 lines
2.7 KiB
ReStructuredText
Introduction
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============
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**mp-units** is a compile-time enabled Modern C++ library that provides compile-time
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dimensional analysis and unit/quantity manipulation. The basic idea and design
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heavily bases on `std::chrono::duration <https://en.cppreference.com/w/cpp/chrono/duration>`_
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and extends it to work properly with many dimensions.
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Thanks to compile-time operations no runtime execution cost is introduced,
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facilitating the use of this library to provide dimension checking in
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performance-critical code. Support for quantities and units for arbitrary unit
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system models and arbitrary value types is provided, as is a fine-grained
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general facility for unit conversions.
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The library architecture has been designed with flexibility and extensibility
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in mind. The demonstrations of the ease of adding new dimensions, their units,
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and unit conversions are provided in the :ref:`Examples`.
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Open Source
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-----------
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**mp-units** is Free and Open Source, with a permissive
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`MIT license <https://github.com/mpusz/units/blob/master/LICENSE.md>`_. Check
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out the source code and issue tracking (for questions and support, reporting
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bugs and suggesting feature requests and improvements) at https://github.com/mpusz/units.
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Approach
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--------
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1. Safety and performance
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- strong types
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- compile-time safety
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- ``constexpr`` all the things
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- as fast or even faster than when working with fundamental types
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2. The best possible user experience
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- compiler errors
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- debugging
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3. No macros in the user interface
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4. Easy extensibility
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5. No external dependencies
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6. Possibility to be standardized as a freestanding part of the C++ Standard
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Library
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With the User's Experience in Mind
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----------------------------------
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Most of the important design decisions in the library are dictated by the requirement of
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providing the best user experience as possible. Other C++ physical units libraries are
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"famous" for their huge error messages (one line of the error log often do not fit on one
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slide). The ultimate goal of **mp-units** is to improve this and make compile-time errors
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and debugging as easy and user-friendly as possible.
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To achieve this goal several techniques are applied:
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- usage of C++20 concepts,
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- using strong types for framework entities (instead of type aliases),
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- limiting the number of template arguments to the bare minimum,
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- :ref:`The Downcasting Facility`.
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.. important::
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In many generic C++ libraries compile-time errors do not happen often. It is hard to
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break ``std::string`` or ``std::vector`` in a way it won't compile with a huge error
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log. Physical Units libraries are different. **Generation of compile-time errors
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is the main reason to create such a library.**
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