functions without implementations
Allow to declare a function by only supplying its type signature. This feature shall enhance rapid prototyping by fixing an interface but leaving some functions unimplemented. Currently this can be (only) simulated by supplying dummy implementations, like f :: ... f = undefined Since it is possible to supply dummy data types by "data T" (not followed by "="), allowing functions without implementations seems almost to be a logical consequence. Surely, the compiler should emit warnings for missing implementations. It would be nice if such function declarations via type signatures could be repeated at any position within a module.