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From: steve@umigw.MIAMI.EDU (steve emmerson)
Newsgroups: comp.lang.c
Subject: Re: swaps with arrays
Message-ID: <112@umigw.MIAMI.EDU>
Date: Mon, 14-Sep-87 10:06:34 EDT
Article-I.D.: umigw.112
Posted: Mon Sep 14 10:06:34 1987
Date-Received: Tue, 15-Sep-87 05:07:03 EDT
References: <2376@zeus.TEK.COM> <110@umigw.MIAMI.EDU> <1361@dataio.Data-IO.COM>
Reply-To: steve@umigw.UUCP (steve emmerson)
Organization: University of Miami
Lines: 39
Summary: summary/analysis of a leaning experience

Let me try to summarize what I think I've learned:

    1) There is some miscommunication going on because some of us are 
       talking about generic *routines* while others are talking about 
       generic *macros*. (I'm guilty of thinking about the former while 
       listening about the latter -- sigh).

    2) In the case of a generic macro, I now agree that the semantics of
       a macro must necessarily be constrained by the language in which
       it is written (which should be obvious) and, therefore, it is 
       unrealistic to ask a generic macro to to something which the language
       does not allow (e.g., using array arguments in a swap macro).  When
       writing generic *macros*, it is ligitimate to expect the user to 
       understand the limitations of the language.  Thus, un-&-able or
       unmodifiable swap arguments are an obvious no-no.  The pitfall here
       is *remembering* that that undistinguished, lower-case routine is 
       actually a macro.

    3) In the case of a generic *routine*, I believe there is no reason to 
       assume that its semantics would necessarily be contrained by the
       language of the *calling* routine (forgive me Walter, I misunderstood
       your original posting -- I thought you were talking about this).
       C programs are full of I/O routines, about whose semantics C
       knows nothing.  Also, it is possible (on some machines) to 
       write a routine in a totally separate language and have it do things 
       C can only dream about (to wax poetic for a second).  I still believe
       generic *routines* are instatiations of abstract algorithms and are 
       (or at least should be) unconstrained.

    4) This whole issue has become *almost* moot (register variables, 
       `consts', bitfields, etc -- sigh) since David Goodenough <343@wrs.UUCP>
       posted his macro/sub-routine hybrid which allows the use of array 
       arguments without the need for an explicit length argument.

Gosh this was (continues to be?) fun!
-- 
Steve Emmerson                     DDN: emmerson@miami.miami.edu
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