The purpose of Cat library is twofold:

  • to provide utility classes and functions that enable the functional programming paradigm in C++.
  • to implement an extensible framework of type classes to attain a better reusability of code through the principles of category theory.


The Cat library:

  • is lightweight. Each function and object shipped with the library takes advantage of modern C++ features, such as constexpr constructs, movability, perfect forwarding, etc.
  • is written in portable C++14 without macro black-magic, whereas template meta-programming is restricted only to the implementation of type traits.
  • implements type traits tailored for generic and functional programming (e.g. is_container, is_associative_container, function_type, function_arity, return_type, is_callable to mention a few).
  • provides utilities, like callable wrappers, which enable functional composition and currying on-top-of any kind of callable types (including std::bind expressions and generic lambdas).
  • provides functions that operate on std::tuple and generic containers.
  • provides utilities that enable perfect forwarding from L/R value containers by means of forward_as and forward_iterator.
  • includes an extensible framework for building type classes and provides the implementation of the following ones:
    • Functor
    • Bifunctor
    • Applicative
    • Alternative
    • Monoid
    • Monad
    • MonadPlus
    • Foldable
    • Show
    • Read
  • includes instances of standard C++14 and Technical Specification (TS) containers/types for the above-mentioned type classes.


At the present moment the Cat library is tested under Linux with both glibcxx and libc++ library and with the following compilers:

  • gcc-4.9
  • gcc-5
  • clang-3.5
  • clang 3.6


The Cat library takes inspiration from the following projects: