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From: levitte@garbo.bion.kth.se (Tommy Levitte)
Newsgroups: comp.lang.c++
Subject: ++ bug ?
Message-ID: <LEVITTE.89Oct14103640@garbo.bion.kth.se>
Date: 14 Oct 89 09:36:40 GMT
Sender: news@sics.se
Distribution: comp
Organization: Royal Institute of Technology, Stockholm
Lines: 68


A few articles ago, somebody talked about extending C++ with the operators ++@
and @++ . I didn't understand the use of it, thinking C++ handled it the right
way anyway.

I wanted to check, though, and made the following test:

// ----------8<-------------------------------------------
#include "stream.h"

class complex
{
	int Re,Im;
public:
	complex() {this->Re=0; this->Im=0;}
	complex(int Re) {this->Re=Re; this->Im=0;}
	complex(int Re,int Im) { this->Re=Re; this->Im=Im;}
	complex operator=(int i) { this->Re=i; this->Im=0; return *this;}
	complex operator++() { return *this=*this+1; }
	complex operator+(int i) { return complex(this->Re+i,this->Im); }
	int re() { return this->Re; }
	int im() { return this->Im; }
};

ostream& operator<<(ostream& foo,complex& bar)
{
  return foo << "(" << bar.re() << "," << bar.im() << ")";
}

main()
{
	complex h,i,j,k;

	h=i=1;
	j=h++; cout << j << " " << h << "\n";
	k=++i; cout << k << " " << i << "\n";
}

//----8<-------------------------------------------------------------

This was compiled (translated, I mean) by AT&T C++ version 1.2 .
The output is the following :

   (2,0) (2,0)
   (2,0) (2,0)


Now, my question is : Is this a bug in version 1.2 or should C++ act like
that ???? It looks like use implemented operator++ always behaves like ++v,
even when you have written v++ !!!!!!

With a "normal" behaviour, the output should be :

   (1,0) (2,0)
   (2,0) (2,0)


Does anybody have an explanation to this ???

Tommy Levitte 
	gizmo@nada.kth.se
	gizmo@kicki.stacken.kth.se
	gizmo@ttt.kth.se
--
Tommy Levitte 
	gizmo@nada.kth.se
	gizmo@kicki.stacken.kth.se
	gizmo@ttt.kth.se