Path: utzoo!attcan!uunet!mcvax!ukc!dcl-cs!aber-cs!pcg
From: pcg@aber-cs.UUCP (Piercarlo Grandi)
Newsgroups: comp.lang.c++
Subject: Re: goodbye cpp ??? (macros vs. inline functions)
Summary: cpp is good for SYNTAX extension...
Message-ID: <265@aber-cs.UUCP>
Date: 24 Nov 88 14:38:03 GMT
References: <6590072@hplsla.HP.COM> <1757@dataio.Data-IO.COM> <3637@pt.cs.cmu.edu> <1304@cod.NOSC.MIL> <12903@duke.cs.duke.edu>
Reply-To: pcg@cs.aber.ac.uk (Piercarlo Grandi)
Distribution: eunet,world
Organization: CS Dept., University College of Wales, Aberystwyth, UK
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X-Disclaimer: Any statement is purely personal.

In article <12903@duke.cs.duke.edu> crm@romeo.cs.duke.edu (Charlie Martin) writes:
    
     I want to throw in one quibble into the discussion of eliminating
     cpp.

     Several people have suggested that eliminating cpp would mean
     giving up conditional compilation, and I want to point out that
     this just isn't so.  There is no reason why the scanner can't
     handle conditional compilation as well, just as comments are
     handled.

Yes, but there is an important area where a macroprocessor is
essential, and is in defining new syntax.

I have a custom, when defining a new data structure such as a list, to
provide a for-like new statement that scans it; I have an habit to
define other innocent syntax extensions, such as new constructs for
recursive descent parsing, or for state machines. If lightly used, and
discreet, syntax extensions can be extremely helpful in making the
program more readable.

There is a big danger here that syntax extensions be used to make
programs even more unreadable and unfamiliar; most people agree that
the original Bourne shell source, where Steven Bourne tried to recreate
the looks of his beloved Algol68C, was not a good idea. I believe that
they have a role when they are used to abstract from the gritty detail,
without trying to later dunamentally the nature of the language they
apply to.

On the other hand I do really believe that cpp in C++ is not that
useful; #include's should be done with import/export, for example, and
definitions can be done with inlines and consts, and conditional
compilation can be done most often by a suitable constant expression in
a if; as to syntax extensions, I think something like ML/1 would be the
ideal thing here.
-- 
Piercarlo "Peter" Grandi			INET: pcg@cs.aber.ac.uk
Sw.Eng. Group, Dept. of Computer Science	UUCP: ...!mcvax!ukc!aber-cs!pcg
UCW, Penglais, Aberystwyth, WALES SY23 3BZ (UK)