Chung-chieh Shan wrote:

Adrien <camaradetux@gmail.com> wrote in article <666572260710241205x19edbd4ar840811b1d7a7315f@mail.gmail.com> in gmane.comp.lang.caml.inria:

7. They easily understand how the standard library is used (but not the
functors), the open statement, the fact that a program may be in several
.ml files. The .mli files are a bit more mysterious. Functors are _very_
mysterious.


Any tips on how (and perhaps how not) to teach functors?  I'm using a
Haskell equivalent of functors (namely constructor classes) in an AI
class (!) and they seem to be mysterious.  It didn't seem to work to
explain the Java/C# code that I would like to write (but can't, because
these languages have no interface _on_ generics (as opposed to generic
interfaces)).

Not sure how well this would work, but my idea would be to map the concepts onto the standard code concepts.

For example,
module type Foo = sig ... end;;
maps to:
type foo = ...;;

module Foo = struct ... end;;
maps to:
let foo = ..;;

module Foo(Bar: Baz) : Quux = struct ... end;;
maps to:
let foo (bar: baz) : quux = ...;;

and so on. Functors, then, are a way to manipulate modules, in the same way that functions are a way to manipulate values.

Brian