LCL type specifications

To: chalin@cs.concordia.ca
Subject: LCL type specifications
From: ymtan@larch.lcs.mit.edu (Yang Meng Tan)
Date: Fri, 15 Jul 94 09:33:28 -0400
Cc: larch-interest@src.dec.com, ymtan@larch.lcs.mit.edu
Delivery-Date: Fri, 15 Jul 94 06:49:19 -0700
In-Reply-To: Patrice Chalin's message of Thu, 14 Jul 94 18:43:53 -0400 <9407142243.aa28505@manitou.cs.concordia.ca>
Reply-To: ymtan@larch.lcs.mit.edu

   Date: Thu, 14 Jul 94 18:43:53 -0400
   From: Patrice Chalin <chalin@cs.concordia.ca>

   > An LCL spec type is local to a specification module.  It is useful if
   > you don't want clients of the module to have access to it.  Spec types
   > need not be implemented.  

   It seems to me that there is a possibility of misinterpretation in Yang Meng's
   statement

	   `Spec types need not be implemented.'
		       ^^^^^^^^

   (Yang Meng can correct me if I'm wrong :-).  Spec types MUST NOT be
   implemented in the sense that they must not be exported by the module.  A
   module can only export non spec constants, types, or functions that are
   explicitly mentioned in the interface specification (at least as far as I
   understand the intended semantics of LCL).

No.  Spec types are there for ease of specifications.  It means that
clients cannot rely on their existence in the implementation.  You can
implement a spec type if you wish, but your clients cannot rely on its
existence because you may decide to remove it in a new implementation.

- Yang Meng Tan

Reference(s):

Re: LCL type specifications

From: Patrice Chalin <chalin@cs.concordia.ca>