tpack is a header-only C++ library that implements types pack (or types list, terminology difference is minor) and various compile-time algorithms on it.
The main difference from most of available alternatives is that tpack is aiming to reduce compile time and compilation memory footprint by minimizing the number of auxillary templates instantiations required to manipulate with a types pack.
Typical C++ implementation of type list relies on classic meta-programming approach based on recursive instantiation of helper template class/struct that implements the algorithm step with explicitly provided partial specialization(s) to stop recursion.
In contrast, tpack heavily uses C++17 constexpr functions and folding expressions for the same purposes and will never trigger recursive helper templates instantiations.
As consequence, algorithms on types are represented as conventional constexpr functions instead of meta-functions which are actually classes with type and/or value members denoting meta-function return type and/or value.
Hence the value-based approach meaning that both arguments to algorithms and resulting type pack are values instead of types in case of meta-functions.
Some algorithms like find_if require a predicate which is a function operating on types, and provide two overloads: first that accepts predicate as constexpr function (corresponding to value-based approach) and second where predicate is specified as meta-function (described as template<typename...> typename Predicate). The second form of API is provided for convenience in terms of direct compatibility with STL type_traits and other meta-functions that user may already have.
Library is inspired by author's experience and ideas from this talk (in Russian): https://www.youtube.com/watch?v=ZUmc45Njs9U