Xref: utzoo comp.lang.c++:7453 gnu.g++:832
Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucsd!helios.ee.lbl.gov!pasteur!agate!WEB.berkeley.edu!c60c-2ca
From: c60c-2ca@WEB.berkeley.edu
Newsgroups: comp.lang.c++,gnu.g++
Subject: What is class <T>Set?
Message-ID: <1990May4.063948.15596@agate.berkeley.edu>
Date: 4 May 90 06:39:48 GMT
Sender: usenet@agate.berkeley.edu (USENET Administrator;;;;ZU44)
Reply-To: c60c-2ca@WEB.berkeley.edu ()
Distribution: usa
Organization: University of California, Berkeley
Lines: 82
X-Local-Date: 3 May 90 23:39:48 PDT


	While looking at some of the files inside the g++-include
directory, I discovered the following "strange" code:

In "Set.hP" ...

#ifndef _<T>Set_h
#pragma once
#define _<T>Set_h 1

#include <Pix.h>
#include "<T>.defs.h"

class <T>Set
{
 private:
  int		count;

 public:
  int		length();

  ....		// Some prototype declarations deleted...

  virtual <T>&	operator() (Pix i) = 0;
  virtual Pix	seek(<T&> item);

  ....		// Rest of body
};

There exists a file called "defs.hP" and in it are the followings:

In "defs.hP" ...

#ifndef _<T>defs_h
#pragma once
#define _<T>defs_h 1

// equality operator
#ifndef <T>EQ
#define <T>EQ(a, b)	((a) == (b))
#endif

// Similiar macros for LE, CMP, HASH ...

And for "Pix.h", it contains the following:

In "Pix.h" ...

#ifndef _Pix_h
#pragma once
#define _Pix_h 1
typedef void *	Pix;
#endif


	As a matter of fact, the extraneous construct "<T> ..."
can be found in all the ".hP" and ".ccP" files under that
directory.

	My first impression is that "<T> ..." has something to
do with 'parametrized type capability'.  I also thought that
the g++ compiler will perform the necessary pre-processing to
substitue the actual type for T.

	However, when I tried to compile a simple program which
includes files "Set.hP" and "Set.ccP", it became evident that
"Set.hP" and "Set.ccP" have to under some pre-processing by a
different pre-processor before they are fed to the g++ compiler.

	My questions then are:

	1)  What is the true meaning of "<T> ..."?  Does it really
	    have something to do with parametrized type?

	2)  Where can I find the pre-processor necessary to convert
	    the ".hP" and ".ccP" files to legal C++ programs?

	Any suggestion or help is GREATLY appreciated.

Andrew Choi
Internet Address:  c60c-2ca@web.berkeley.edu
Standard Disclaimer