Allow to declare a function by only supplying its typesignature.This feature shall enhance rapid prototyping by fixingan interface but leaving some functions unimplemented.Currently this can be (only) simulated by supplyingdummy implementations, like f :: ...f = undefinedSince it is possible to supply dummy data types by"data T" (not followed by "="), allowing functionswithout implementations seems almost to be a logicalconsequence. Surely, the compiler should emit warningsfor missing implementations.It would be nice if such function declarations via typesignatures could be repeated at any position within amodule.