You don't have to have them completely fleshed out. But you do have to have them fleshed out to the type level. The Haskell compiler can be an invaluable aid

You don't have to have them completely fleshed out. But you do have to have them fleshed out to the type level. The Haskell compiler can be an invaluable aid in fleshing out the design of problems. Especially when they are complex difficult to wrap your head around.