From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <2ce618c636a8a74af13258cdeaa93de0@plan9.jp>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Include guards and multiple includes
From: Joel Salomon <chesky@plan9.jp>
Date: Mon, 23 Oct 2006 15:12:17 -0400
In-Reply-To: <e44be67fc6736d0e097e632a0cebdba9@terzarima.net>
MIME-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Topicbox-Message-UUID: d33187e4-ead1-11e9-9d60-3106f5b1d025

> > ?c only recognize 9
> > preprocessor symbols:
<snip>
>=20
> and that's easily more than too much

When metaprogramming techniques are needed, should we have the C
preprocessor or are we going to get a better tool?  (I know!  I know!
C++ templates!  =E2=98=BA)

I=E2=80=99ve needed the full-power preprocessor in the past, when I had t=
o
implement a miniature function-generating and function pointer table
populating mini-language (and it really was the most readable,
debuggable, and maintainable implementation of the spec possible).  I
didn=E2=80=99t need the various #ifs, but I did need ANSI-type macro
expansion; IIRC, ?c=E2=80=99s is different enough=E2=80=94and not so well=
 documented
(looking at the implementation of the assert macro; how do you do
symbol catenation, or conversion to a string?)=E2=80=94that an implementa=
tion
of this trick would need subtle rewriting.

I don=E2=80=99t know if a =E2=80=9Cgood=E2=80=9D metaprogramming/code gen=
eration tool is
possible for a language with syntax more complicated than Lisp=E2=80=99s,=
 but
even CPP has its use.

For the sort of conditional compilation admitted by =E2=80=9C#ifdef Consi=
dered
Harmful=E2=80=9D, what minimal set of CPP symbols would suffice?

--Joel