Xref: utzoo comp.object:507 comp.lang.c++:5679
Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!swrinde!cs.utexas.edu!uunet!microsoft!jimad
From: jimad@microsoft.UUCP (Jim Adcock)
Newsgroups: comp.object,comp.lang.c++
Subject: Re: Dumb question
Message-ID: <9191@microsoft.UUCP>
Date: 28 Nov 89 17:53:48 GMT
References: <61737@aerospace.AERO.ORG> <9938@june.cs.washington.edu> <2122@tukki.jyu.fi> <2159@tukki.jyu.fi>
Reply-To: jimad@microsoft.UUCP (Jim Adcock)
Organization: Microsoft Corp., Redmond WA
Lines: 125

// in any case -- here's a quick and dirty example of what I think 
// people have been talking about....

#include <stdio.h>
#include <string.h>

void Fatal() 
{ fprintf(stderr, "Smalltalk-like runtime error\n"); exit(1); }

char* base__classname = "base";
class base
{
public:
	virtual char* classname() {return base__classname; }
	virtual int compare(base& b)
	{if (classname() != b.classname()) Fatal(); else return 0;}
	virtual base& print() {printf("base\n"); return *this;}
	friend int operator==(base& a, base& b){return a.compare(b)==0;}
	friend int operator!=(base& a, base& b){return a.compare(b)!=0;}
	friend int operator>=(base& a, base& b){return a.compare(b)>=0;}
	friend int operator<=(base& a, base& b){return a.compare(b)<=0;}
	friend int operator>(base& a, base& b){return a.compare(b)>0;}
	friend int operator<(base& a, base& b){return a.compare(b)<0;}
};

char* Int__classname = "Int";
class Int : public base
{
	int i;
public:
	Int(int ii) { i = ii; }
	base& print(){ printf("%d\n",i); return *this;}
	char* classname() { return Int__classname; }
	int compare(base& b) 
	{if (b.classname() != classname()) Fatal(); else return i-((Int*)&b)->i;
	}
};

char* Double__classname = "Double";
class Double : public base
{
	double i;
public:
	Double(double ii) { i = ii; }
	base& print(){ printf("%g\n",i); return *this;}
	char* classname() { return Double__classname; }
	int compare(base& b) //this is a slightly bogus def for "compare":
	{ if (b.classname() != classname()) Fatal(); 
	  else return (int)(1.0e10*(i-((Double*)&b)->i));
	}
};

char* String__classname = "String";
class String : public base
{
	char* i;
public:
	String(char* ii) { i = ii; }
	base& print(){ printf("%s\n",i); return *this;}
	char* classname() { return String__classname; }
	int compare(base& b)
	{ if (b.classname() != classname()) Fatal(); 
	  else return strcmp(this->i, ((String*)&b)->i); 
	}
};

class List4	//cheap imitation of a "real" list class
{
  	base* p[4];
public:
	List4(base* p0, base* p1, base *p2, base *p3) 
	{p[0]=p0; p[1]=p1; p[2]=p2; p[3]=p3;}
	List4& print();
	List4& sort();
};

List4& List4::print()
{
	printf("(\n"); 
	for (int i=0; i<4; ++i) p[i]->print(); 
	printf(")\n"); 
	return *this;
}

List4& List4::sort()	//bogus
{
	for (int j=0; j<3; ++j) for (int i=0; i<3; ++i)
		if (*p[i] > *p[i+1])
		{
			base* tmp = p[i];
			p[i] = p[i+1];
			p[i+1] = tmp;
		}

	return *this;
}

main()
{
	Int i6(6);
	Int i5(5);
	Int i_100(-100);
	Int i200(200);
	Int i5a(5);
	Double d5(5);
	Double d6(5);
	String himom("hi mom");
	String hidad("hi dad");
	String hibro("hi bro");
	String hisis("hi sis");
	String hidad2("hi dad");
	printf("%d\n", i5 == i5a);
	printf("%d\n", i5 > i6);
	printf("%d\n", i5 == i5);
	printf("%d\n", d5 < d6);
	printf("%d\n", d5 == d5);
	printf("%d\n", himom == hidad);
	printf("%d\n", hidad == hidad2);
	printf("%d\n", hidad > himom);
	List4 L1(&himom, &hidad, &hibro, &hisis);
	L1.print().sort().print();
	List4 L2(&i6, &i5, &i_100, &i200);
	L2.print().sort().print();
	printf("%d\n", i5 > himom);	//ack! compare of unlike objects!
}


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