The Many Faces of Number ⟷ String Conversions

Seemingly a basic task, converting between numbers and their string representation is a problem which has kept C++ busy since its birth.

C++ inherited several library functions from C dealing with such conversions and has kept adding more on almost every new standard, the latest examples being to/from_chars from C++17 and C++20’s format library. This didn’t stop non-standard libraries, like Boost, from offering even more ways to do those conversions.

In this talk we will explore

• std::atoi
• std::stoi
• std::to_string
• std::from_chars
• boost::lexical_cast
• std::scan

and more. We will try to understand why the number-string conversion problem is being solved repeatedly, compare the API, implementation and performance of these utilities and see that, even now, there still room for improvement.