Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hplsla!jima
From: jima@hplsla.HP.COM (Jim Adcock)
Newsgroups: comp.lang.c++
Subject: Re: Allowing only one instantiation of a class
Message-ID: <6590297@hplsla.HP.COM>
Date: 12 Oct 89 17:48:48 GMT
References: <672@suntops.Tops.Sun.COM>
Organization: HP Lake Stevens, WA
Lines: 32

//heres one approach:

extern "C" 
{
  int printf(char* p, ...);
  void exit(int condition);
};

class oneonly
{
  const char* const nm;
  static int oneexists;
public:
  oneonly(const char* const name):nm(name)
  {
    if (oneexists) {printf("Sorry: oneonly already exists\n"); exit(1);}
    else           printf("this is the one and only oneonly: %s\n",nm);
    oneexists=1;
  }
};

int oneonly::oneexists=0;

// Lets see what happens when we try this: ---------------------------------

oneonly theFirstOne("theFirstOne");

void main()
{
  oneonly theSecondOne("theSecondOne");
  oneonly* p = new oneonly("new_oneonly");
}