RealWorld -is:package
base Control.Monad.ST Control.Monad.ST.Lazy Control.Monad.ST.Lazy.Safe Control.Monad.ST.Safe GHC.Exts,
ghc-prim GHC.Prim,
primitive Control.Monad.Primitive,
foldl Control.Foldl,
proto-lens Data.ProtoLens.Encoding.Growing,
rebase Rebase.Prelude,
massiv Data.Massiv.Array.Mutable,
mutable-containers Data.Mutable,
stateref Data.StateRef.Instances,
massiv-test Test.Massiv.Utils,
declarative Numeric.MCMC,
pvar Data.Primitive.PVar RealWorld is deeply magical. It is primitive, but it
is not unlifted (hence ptrArg). We never manipulate
values of type RealWorld; it's only used in the type system,
to parameterise State#.