Haskell package Not on Stackage, then how?

Question

I want to use HList: Heterogeneous lists, but the package seems not on Stackage.

I currently use stack. In this case what is the option besides going back to use Cabal?

Answer 1

Use extra-deps in stack.yaml:

extra-deps:
- HList-0.5.2.0

Stack should prompt you to if you add the package as a dependency in the Cabal file.