Compile Time Regular Expressions is a header-only C++ library that evaluates regular expressions at compile time using constexpr.
The library solves the problem of runtime regex overhead by moving pattern matching into the compilation phase. It uses C++ template metaprogramming and constexpr functions to parse and execute regular expressions during compilation, producing zero-runtime-cost pattern matching when patterns are known at build time. The approach supports a PCRE-compatible syntax and allows developers to write regex patterns as compile-time constants, with results available as compile-time values.
Projects with fixed, known regex patterns benefit most from this tool, particularly performance-critical applications where eliminating runtime regex evaluation matters. Embedded systems, real-time processing, and compile-time validation scenarios are natural fits. The library works as a header-only dependency requiring only C++17 or later, making integration straightforward. Developers should adopt this when their regex patterns are determined at compile time; if patterns must be dynamic or user-supplied at runtime, traditional regex libraries remain necessary.
The project shows consistent refinement of its constexpr implementation across C++ standard versions. Development maintains active engagement with the C++ standards evolution, particularly around constexpr capabilities. The codebase demonstrates careful attention to compile-time evaluation constraints and template instantiation patterns. Work reflects a focus on expanding pattern syntax support and improving the compile-time evaluation model as language features mature.
