Path: utzoo!attcan!uunet!mcsun!inria!litp!geocub!anthes
From: anthes@geocub.greco-prog.fr (Franklin Anthes)
Newsgroups: comp.lang.c++
Subject: Getting a string class to work.
Message-ID: <1760@geocub.greco-prog.fr>
Date: 20 Mar 90 13:31:01 GMT
References: <1759@geocub.greco-prog.fr>
Reply-To: anthes@geocub.greco-prog.fr (Franklin Anthes)
Organization: Greco-Programmation, Bordeaux, France.
Lines: 60


I'm just starting out with C++. I want to build a very basic String
class. 

BTW I wonder why such basic classes as String, etc. standard in C++?
It is a good idea of course to do something like this once or twice during
the learning process, but reinventing each wheel can become tedious after
a while.

Anyway, here's a small piece of my code :

typedef unsigned long StringLenType;

class String {
        char *buf;
        StringLenType len;
public:
        String();
        String(const char *);
        String(const String &);
        ~String();
        String& operator=(const String&);
        friend String& operator+(String&,String&);
}

String& String::operator=(const String& s) {
        len = s.len;
        delete buf;
        buf = new char[len+1];
        strcpy(buf,s.buf);
        return *this;
}

String& operator+(String& s1,String& s2) {
        String*& ret = new String( s1.len + s2.len );
        memcpy(ret->buf,s1.buf,s1.len);
        memcpy(ret->buf+s1.len,s2.buf,s2.len+1);
        return *ret;
}

I want to implement operations like :

 String s1;
 String s2("foo");
 String s3("bar");

 s1 = s2 + s3; // s1 == "foobar"

Now the code above "works", but the space allocated by operator+ is not
deleted. Is there an elegant way to do this sort of thing in C++?

A possible solution (kludge) would be to add a tag into the String class,
to indicate whether the string is a temporary which should be deleted after
the result is calculated. Hmm garbage collection can come in handy sometimes.

A big merci, for those willing to help me me out.
-- 

	Frank Anthes-Harper :  Bien le bonjour de la France
	anthes@geocub.greco-prog.fr