Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!uakari.primate.wisc.edu!uflorida!novavax!weiner
From: weiner@novavax.UUCP (Bob Weiner)
Newsgroups: comp.lang.eiffel
Subject: Re: BASIC TYPES
Message-ID: <1799@novavax.UUCP>
Date: 21 Feb 90 00:00:31 GMT
References: <1864@clyde.concordia.ca> <251@eiffel.UUCP>
Organization: Motorola Inc.
Lines: 27
In-reply-to: bertrand@eiffel.UUCP's message of 20 Feb 90 06:14:10 GMT

> 	As a result, the basic types are treated as ``quasi-normal'' in the
> release available since last summer (2.2). Internally, however, they are
> still handled specially so as to guarantee a high level of efficiency
> (3 + 4 is theoretically a routine call, but few Eiffel users would want it
> to be implemented that way!). In fact, this part is one of the trickiest in

I do not agree with this statement since I believe that one cannot
inherit from the basic types in order to create a new class which
constrains the type's invariant further.  (I must admit that I have
tried to inherit from INT rather than INTEGER, and so forth, since there
is no class interface corresponding to INTEGER.)

Rather than sprinkle pre- and post-conditions around routines that say:

	require
	   param > 0

and other such things, it makes sense to create classes for POS_INT,
NON_NEG_INT and so forth and then type the formal parameters of the
routines.  The current implementation does not support this basic idea
and hence event the term 'quasi-normal' seems too strong to me.

I do hope that Eiffel V3.0 will correct this limitation.  Even better, I
would enjoy finding out that I am mistaken in my view.
-- 
Bob Weiner, Motorola, Inc.,   USENET:  ...!gatech!uflorida!novavax!weiner
(407) 364-2087