Re: [Caml-list] [Question] Loading .ml in memory to interact with them.

[Evgeny Roubinchtein <zhenya1007@gmail.com>]

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Just to be clear: does this need to work on Windows, or only on Unix-like
systems?  If it only needs to work under Unix, then your problem sounds to
me like a standard inter-process communication problem with the usual
solutions being to use a combination of pipe(), dup2(), and select() system
calls, and with the alternative solution being to use a pseudo-terminal.
Chapter 5 of "Unix System Programming in OCaml"
https://ocaml.github.io/ocamlunix/pipes.html should give you some guidance
on implementing the former solution.  If you want to use pseudo-terminals,
I don't know of a freely-available tutorial-style reference off the top of
my head.  "Advanced Programming in the Unix Environment" by late Richard
Stevens has had a chapter dedicated to pseudo-terminals since the first
edition of the book: perhaps your local library has a copy.  Failing that,
you could read Linux man page for pty(7), and follow the links to forkpty
and friends.  For example, you could start here:
http://man7.org/linux/man-pages/man7/pty.7.html.

The fact that you want to do all of this from Matlab is an extra challenge,
but I don't think it's an insurmountable challenge.  Even if Matlab doesn't
have the functions you need "out of the box", it is possible to extend
Matlab with C code, so you could implement a C function to initialize the
external process, and another function to send to the external process and
receive results.  The following is probably a good starting point for
learning how to extend Matlab with C/C++:
https://www.mathworks.com/help/matlab/call-mex-files-1.html.  I don't know
off the top of my head if Matlab already comes with sufficiently flexible
functionality for communicating with an external process: you could try
searching the documentation and/or engaging Mathworks technical support
(assuming your license comes with technical support) and/or asking on
Mathworks forums.

-- 
Best of luck
Zhenya

On Thu, Mar 23, 2017 at 5:37 AM, <paul.lachat@edu.univ-fcomte.fr> wrote:

> Hello,
>
> I need to find a way to put Ocaml program in memory so I could interact
> with the program
> (call function, get result, find information about the variables, ...)
> without always reading the file.
>
> That what append when we use the directive #use "file.ml";; in the
> interactive shell (the toplevel, when you type the command ocaml in a
> shell).
>
> The instruction need to come from a Matlab function. So, I was thinking to
> create a process who run the ocaml command,
> redirect his standard input in a named pipe, redirect his standard output
> in another named pipe, so I could send instructions and received responses.
>
> But when I send the first instruction (ex : #use "file.ml";;\n), the
> ocaml process send back the response and stop.
>
> ____
>
> file.ml :
> let x = 10;;
>
> ____
>
>                    "#use "file.ml";;\n"
> Matlab --   /tmp/pipe_in  -->   ocaml
>
>                    "val x : int = 10"
> Matlab <-- /tmp/pipe_out --    ocaml
>                                                   then ocaml stop...
>
> ___
>
>
> So I would like to know if you think it's a good solution and if it is, do
> someone know how could I make it work ?
>
> _
>
> I've tried another solution. I use Unix.fork() and launch, in the son
> process, the ocaml command then
> I send instructions from the father process to the son process with anonym
> pipe (Unix.pipe()).
>
> But here I have trouble with blocking read, I send an instruction, read
> the answer but even if I've read all char of the answer, it's wait to read
> more but there is no more to read...
>
> I have tried to use Unix.set_nonblock() and catch EAGAIN, but then I don't
> get anything at all in the buffer given to Unix.read().
>
> If someone could help, I would be grateful !
> Lachat Paul
>
>

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