Re: [Caml-list] a question about Ocaml toplevel behavior

["Nicolás Ojeda Bär" <nicolas.ojeda.bar@lexifi.com>]

Hello,

I don't know if there is any deep design reason for this behaviour,
but for one it enables a kind of information hiding: in order to hide
modules which are private to a library and should not be exposed to
the client code, simply do not install the corresponding .cmi files.

Best wishes,
Nicolás


On Sun, Mar 11, 2018 at 4:51 PM, Matej Košík <mail@matej-kosik.net> wrote:
> Hi Nicolás,
>
> Thank you for the reply.
>
> On 03/11/18 16:06, Nicolás Ojeda Bär wrote:
>> Hello Matej,
>>
>> My understanding is that the compiler will delay opening a .cmi file
>> until absolutely necessary.> Since it does not need to look into Location in order to compile the
>> given phrase, the .cmi is not opened and the type Location.t remains
>> abstract. But if you give the compiler an excuse to open location.cmi
>> then the definition of the type Location.t will become known to the
>> compiler and the toplevel will be able to print the values concretely.
> I see some of the disadvantages of this behavior:
>
>   (0) I have lost time wondering why things are printed as "<abstr>" instead of the real thing.
>
>   (1) "<abstr>" may (confusingly) mean something else than "a value of an abstract type".
>       It may mean that "toplevel has find an excuse not to load a relevant *.cmi file some so it does not know (yet) how to print a given value.
>       (this is very unintuitive)
>
>   (2) #install_printer directive may have no effect if toplevel has find an excuse not to load relevant *.cmi file.
>       (this is very unintuitive)
>
> Was this done on purpose? What do we gain from this behavior?
> (considering that computer time (as opposed to human time) has ~zero value).