I do that thing, where I just start coding from scratch. Example: When programming in haskell, I just write the types (not always) and undefined most things

I do that thing, where I just start coding from scratch. Example: When programming in haskell, I just write the types (not always) and undefined most things and only then I start implementing. Whenever I make a new function, it gets composed by a bunch of other functions that are not yet implemented (undefined's) and eventually this converges. Refactoring is then based on equality principles in my head. Yeah, it fails sometimes, but that's why pure functions and type safety feels so important sometimes.