From: Yaron Minsky <yminsky@gmail.com>
To: caml-list@inria.fr
Subject: [Caml-list] A limitation of "with type" declarations for first-class modules
Date: Tue, 20 Sep 2011 09:36:25 +0800 [thread overview]
Message-ID: <CADKNfhL2eqV3aSF76yy6rigPVfj+MXhjzh_b_xizbwdt3P_QZg@mail.gmail.com> (raw)
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For some reason, 1st-class modules have more restrictive "with" syntax,
which turns out to be a practical problem.
The main constraint is that with constraints do not seem to be able to refer
to sub-modules. Consider the following code snippet:
> module type Foo = sig type t end
> module type Bar = sig module Foo : Foo end
>
> (* compiles *)
> let g (type a) (m : (module Foo with type t = a)) = ()
>
> (* fails to compile with a syntax error *)
> let f (type a) (m : (module Bar with type Foo.t = a)) = ()
Of course, ordinary modules have no such constraint. Any thoughts as to
what is going on here, and whether it can be fixed? This has really
restricted designs I've been using, forcing me to flatten out structures
that are more naturally nested.
y
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next reply other threads:[~2011-09-20 1:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-20 1:36 Yaron Minsky [this message]
2011-09-20 8:00 ` Jacques Le Normand
2011-09-20 8:10 ` Yaron Minsky
2011-09-20 9:03 ` Alain Frisch
2011-09-20 9:23 ` Jacques Le Normand
2011-09-20 10:07 ` Yaron Minsky
2011-09-20 10:13 ` Yaron Minsky
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