Run it once. Keep the result.

callonce wraps any C++ callable, executes it at most once per argument set, and caches what it returns. std::call_once with a return value, a reset, an argument-sensitive cache, and a choice of a zero-overhead or a lock-free policy. Header-only, MIT, C++20.

One wrapper, every callable

One wrapper, every callable A single class template — memoized_invoke — takes free and member functions, lambdas, functors, std::function and std::bind_front results. CTAD deduces everything; there are no manual template arguments.

Pick your synchronisation

Pick your synchronisation single_threaded is a bare enum with no overhead. lock_free is an atomic CAS plus C++20 atomic::wait — exactly one thread runs the callable, the rest block until the value is ready.

MIT licensed Permissive, no strings attached. Use it in commercial or open-source projects. The full text ships in the source archive and in the header itself.

Version 1.0.0 C++20, one header, no dependencies beyond the standard library. Builds standalone with CMake, embeds via add_subdirectory, or comes in through Conan.