singletons-base uses singletons-th to define promoted and singled functions from the base library, including the Prelude. This library was originally presented in Dependently Typed Programming with Singletons, published at the Haskell Symposium, 2012. (https://richarde.dev/papers/2012/singletons/paper.pdf) See also the paper published at Haskell Symposium, 2014, which describes how promotion works in greater detail: https://richarde.dev/papers/2014/promotion/promotion.pdf. . WARNING: singletons-base defines orphan instances for Sing, SingKind, etc. for common types such as Bool, [], Maybe, etc. If you define instances of these types in your code, you will likely not be able to use that code with singletons-base. . singletons-base uses code that relies on bleeding-edge GHC language extensions. As such, singletons-base only supports the latest major version of GHC (currently GHC 9.14). For more information, consult the singletons README. . You may also be interested in the following related libraries: . * The singletons library is a small, foundational library that defines basic singleton-related types and definitions. . * The singletons-th library defines Template Haskell functionality that allows promotion of term-level functions to type-level equivalents and singling functions to dependently typed equivalents.