About flute

What is flute?

Flute is a C++20 fixed-point library. It aims to provide a modern interface that allows to deal with fixed-point arithmetic. It is meant to be used on systems that don't have an FPU (floating-point unit), such as micro-controllers.

Flute is a bit different from other fixed-point libraries. It includes utilities for look-up tables (LUT, hence the name "flute").

Basic example

Here is a simple example that shows how to use the library:

#include "flute.hpp"

int main()
{
  using namespace flute;

  constexpr ufixed<16,16> pi{3.1415926};
  constexpr auto two_pi = 2 * pi;

  static_assert((two_pi - pi).as<double>() == pi.as<double>());
}

Features

• Zero-overhead: You only pay for what you need. For instance (real-world example), compiling for an ARM Cortex-M3 using GCC 13.2, flute allows to multiply an integer and a ufixed<12, 20> as fast as a regular 32-bit integer multiplication. Compared to multiplying an integer with a 32-bit float, this allows to save about 1277 bytes in the compiled firmware.
• Embedded-friendly: The STL is not required. Flute only needs a few C++ headers: array, concepts, limits, and type_traits.
• Modern C++ standards: Requires C++20. Concepts make the code more reliable and provide readable error messages. Moreover, modern C++ is key to achieve optimal performance.
• Compile-time evaluation: Everything is constexpr! This has a very positive impact on performance too.
• Header-only library: No need to link the library, simply include flute.hpp into your .cpp files.
• Policy-based design: Some fixed-point operations require to make choices, especially regarding overflow.

How to use

Prerequisites

Since this is a header only library, all you need is a C++20 compiler. This library has only been tested with GCC 13.2 (x86-64 and arm-none-eabi). It should compile with GCC 10 and Clang 16.

Using the library

Flute is a header-only library, so all you need to do is include flute.hpp into your C++ files.