Lambda the Ultimate

A nice post from Oleg on the Haskell mailing list shows how to implement high order modules, and more specifically translucent applicative functors in idiomatic Haskell.

Thus different instantiations of the functor with respect to type-compatible arguments are type-compatible; and yet the functor hides the representation details behind the unbreakable abstraction barrier.

The work is inspired by (our own) Ken Shan's work that can be found here.

Oleg concludes,

The example illustrates that Haskell already has a higher-order module language integrated with the core language and with the module checking being a part of the regular typechecking.

Jayadev Misra's tribute to EWD at Europar-2003.

A short essay that may be relevant to the question whether language designers should make their languages more forgiving as regards programmer errors, or more stringent.