[Caml-list] unwind-protect

[Jason Hickey <jyh@cs.caltech.edu>]

A related, but pragmatic problem.  Suppose we have some imperative code, 
and we need an "unwind-protect" operation.  Consider this code to make 
sure a file is closed after it is used.

let with_open_file (name : string) (f : in_channel -> unit) =
    let inc = open_in name in
       try
          f inc;
          close inc
       with
          exn ->
             close inc;
             raise exn

1. It would be wonderful to have a "finally" clause, so we don't have to 
duplicate the close operation.  I suppose we can fake it with CamlP4, 
but it seems better built-in.

2. This kind of exception re-raising does not work well with stack 
tracing (OCAMLRUNPARAM=b).  It would be very nice to add a "finally" 
clause that did not interfere with stack tracing, or make it so that 
re-raising would preserve the location where the exception was created.

Jason

-- 
Jason Hickey                  http://www.cs.caltech.edu/~jyh
Caltech Computer Science      Tel: 626-395-6568 FAX: 626-792-4257

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