Re: [Caml-list] Warnings opening modules (was: why is building ocaml hard?)

[Hendrik Boom <hendrik@topoi.pooq.com>]

On Fri, Jul 15, 2016 at 10:52:38AM +0100, David Allsopp wrote:
> Goswin von Brederlow wrote:
> 
> I don't follow what you mean - what I propose changing is that [open Util]
> would cause a warning and eventually, in some future version of OCaml, be
> rejected by the compiler. The problem it would solve is that
> ocamldep/whatever knows that open Foo always refers to a toplevel (or fully
> qualified) module path.
> 
> > A (for me) more common code would be:
> > 
> >     open ReallyCoolLibraryPack
> >     (* myriad more open statements *)
> > 
> >     Util.foo bla baz
> >     module Bla = Util.MAKE(M : FOOABLE)
> > 
> > You still get the same dependency on ReallyCoolLibraryPack.Util,
> > ReallyCoolLibraryPack.Util.MAKE, ReallyCoolLibraryPack.FOOABLE, ...
> > without successive opens.
> 
> Indeed, that's my preference, although I'm stupidly picky and actually
> prefer to write:
> 
> module Util = ReallyCoolLibraryPack.Util
> 
> but that comes under my list of "strange habits which normal people don't
> agree with" :o) I'm allergic to anything which involves a wildcard ([open
> ReallyCoolLibraryPack] being rather too like writing [import
> ReallyCoolLibraryPack.*;])

And that's a real problem -- that fact that openning a module can fill 
the namespace with lots of stray identifiers, which the user does not 
control.

It may reduce the amount of code you have to write.

But it makes the code unstable in the long run, and it makes it hard to 
read.  The naive reader will encounter identifiers and have no idea 
where to look for their definitions.

It's not just a problem with modules that define modules.  It'a a 
problem with modules that define anything.

To alleviate this, either specify explicitly what names you are 
accepting definitions of when you open a module, or, after you open a 
module, mention the module name very time you use one if its defined 
names, as, Module.name instead of just name.

And make the compiler check this.  Withiut a constraint like this, I 
find much OCaml code incomprehensible.

Or is there some kind of code browsing tool that explicates all this?

-- hendrik