Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!gatech!hubcap!billwolf%hazel.cs.clemson.edu
From: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu (William Thomas Wolfe,2847,)
Newsgroups: comp.lang.misc
Subject: Re: Escape from strong typing
Message-ID: <6372@hubcap.clemson.edu>
Date: 1 Sep 89 19:44:14 GMT
References: <14500@haddock.ima.isc.com>
Sender: news@hubcap.clemson.edu
Reply-To: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu
Lines: 26

From karl@haddock.ima.isc.com (Karl Heuer):
> An lvalue take-as operator is one of the few "universal escapes" that is 
> not provided by C, and is not easy to fake for the general case.  (I 
> believe it's Modula-2 that has this feature as a builtin operator 
> named ESCAPE.)

    Actually, according to my Modula-2 manual (which is the "second,
    corrected edition"; I think there's now a "third, corrected edition"),
    Modula-2 provides type transfer functions which do not involve the
    generation of any machine instructions, and which carry the name of
    the type being converted to.  Any representation differences between
    the two types would presumably have to be addressed via an encapsulating
    procedure which performed the necessary transformations.

    Ada provides Unchecked_Conversion, which essentially does the same
    thing except for the fact that any use of Unchecked_Conversion will
    immediately flag your program as potentially non-portable; standard
    type conversion functions exist carrying the name of the type which
    are guaranteed to be portable, but they only cover the predefined types.

    Modula-2 "second, corrected edition", doesn't seem to be overly concerned
    with identifying potential portability problems, although this may have
    been addressed in the "third, corrected edition".  


    Bill Wolfe, wtwolfe@hubcap.clemson.edu