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[Caml-list] Catching errors (Unix-Module)
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Date: -- (:)
From: Oliver Bandel <oliver@f...>
Subject: [Caml-list] Catching errors (Unix-Module)
Hello,

I'm experimtnzing with the Unix-module and try to
cath Unix-errors.

Look here:


=============================================
oliver@first:/home/oliver > unix-top 
        Objective Caml version 3.01

# Unix.stat "/foo/bar";;
Uncaught exception: Unix.Unix_error (Unix.ENOENT, "stat", "/foo/bar").
# 
=============================================

How to handle such Errors?

I tried this one:

=============================================
# try Unix.stat "/foo/bar" with Unix.Unix_error -> "shi...";;
Characters 30-45:
The constructor Unix.Unix_error expects 3 argument(s),
but is here applied to 0 argument(s)
#
=============================================

I looked into the reference-Handbook and found that
the unix-error is of type

  error * string * string


So, when i look into the line 
 "Uncaught exception: Unix.Unix_error (Unix.ENOENT, "stat", "/foo/bar")."

the part "(Unix.ENOENT, "stat", "/foo/bar")" looks like
the error*string*string.

But how to handle this?

What actions can I use here?
I may want to ignore some of those errors under some conditions,
but I also may want to handle them.

What about the type of the error?
I understand how normal functions have to be designed
in respect to their types.

But I don't understand, how exceptions will be handled
in respect of their types.
Some days ago I tried some simple examples and thought
that I had understand the exception-system of OCaml,
but now, when doing "real word"-programming,
I realize that I didn't understand it.


So, please help.


TIA,
  Oliver

P.S.: When defining an exception that already exists (Division_by_zero for
      example), the exception can't be catched with try (at least this problem
      occured with OCaml 3-.01 on Linux).


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