Is there Liquid Haskell enabled Prelude?

Question

Is there a annotated variant or Haskell Prelude available for easy migration of existing programs that call functions like head or length?

Answer 1

As discussed in the LH Documentation, you can augment existing files with .spec files that give just specifications of already existing code. LH itself comes with a large prelude (see the include folder) that includes specifications for lots of common stuff, including head, length, functions on Data.Set, etc.