notcpp is a library that attempts to provide an alternative to using CPP as a mechanism for conditional compilation. It provides facilities for determining if specific names or class instances exist and responding accordingly. When a value or class instance appears between minor releases of a third-party package, a common way of dealing with the problem is to use CPP to conditionally use one block of code or another. The trouble with CPP is it's hard to statically analyse: tools based on haskell-src-exts will outright refuse to parse it, for example. It turns out Template Haskell will do the same job in some cases. notcpp is largely a proof-of-concept, experimental package: you are welcome to use it if it suits you, but it may be liable to change suddenly.