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Date: Mon, 5 Oct 1998 18:27:18 +0400 (MSD)
From: Anton Moscal <msk@post.tepkom.ru>
To: caml-list@inria.fr
Subject: Local definitions
In-Reply-To: <199809280951.LAA27562@pauillac.inria.fr>
Message-ID: <Pine.LNX.4.03.9810051823001.28401-100000@post.tepkom.ru>
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Hello!

Why CaML doesn't not allow the following style of local definitions:

declare
   <definition> ...
in
   <expression>

with following translation:

let module Temp = struct 
  <definition>... 
  let result = <expression> 
end in
  Temp.result

or, the second variant: simply allow declaration of
types, exceptions, open statements and others in "let-in"
expressions with the same translation:

let find x vec =
  let exception Return of int in
  try 
    Array.iteri (fun i elem -> if elem = x then raise (Return i)) vec;
    None
  with
    Return i -> Some i
  
can be translated as:

let find x vec =
  let module T = struct
    exception Return of int
    let res = 
      try 
	Array.iteri (fun i elem -> if elem = x then raise (Return i)) vec;
	None
      with
	Return i -> Some i
  end in T.res


This syntax allow more convenient notation for local types,
classes, exceptions and others definitions, than explicit usage of 
local modules.

Anton E. Moscal   msk@vvv.niimm.spb.ru