Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!uunet!snorkelwacker.mit.edu!linus!linus!mbunix!mmk From: mmk@d62iwa.mitre.org (Morris M. Keesan) Newsgroups: comp.std.c++ Subject: Re: sizeof('a') Message-ID: Date: 20 Jun 91 19:49:32 GMT References: <1991Jun18.210440.16325@csc.ti.com> Sender: news@linus.mitre.org (News Service) Distribution: usa Organization: The Mitre Corp., Bedford, MA. Lines: 46 In-Reply-To: bmk@m2.csc.ti.com's message of 18 Jun 91 21:04:40 GMT Nntp-Posting-Host: d62iwa.mitre.org In article <1991Jun18.210440.16325@csc.ti.com> bmk@m2.csc.ti.com (Brian M Kennedy) writes: > . . . being consistent with C would have been a strong enough reason > for Bjarne to have made the type of 'c' be int in the first place, > EXCEPT that there is a stronger reason to have 'c' be char in C++: > overloading. > > If I write: > > cout << 'A'; > cout << 65; > > I want overload resolution to choose operator<<(ostream&, char) for > the first call and operator<<(ostream&, int) for the second. If 'A' > was type int then the first call would print the int value of A rather > than the character A. That would be very ugly. > > This is discussed by E&S (ARM) on p.9, 2.5.2, in the annotations. The reason for 'a' to be a char is indeed for overload resolution to work, as discussed in the ARM in 2.5.2, but the example given above is not a good example. In fact, in the implementations I'm familiar with (and I haven't used 2.0, so I don't know if it's still true), cout << 'A' prints the int value of A. See "The C++ Programming Languange" by Stroustrup, 1987 edition. On p. 9, 8.2.1, we see class ostream defined with operator<<(char*) and operator<<(int), but no operator<<(char), and two pages later, on page 229, we see ---------------------------------------------------------------------- There are no character valued expressions in C++. In particular, '\n' is an integer (with the value 10 when the ASCII character set is used), so that cout << "x = " << x << '\n'; writes the number 10 and not the expected newline. ---------------------------------------------------------------------- The ARM does not address this issue, leaving ostreams, cout, and overloaded << operators as a library issue rather than a language issue. What do 2.0 implementations do with this? Is this an incompatibility that will cause problems for C++ 1.2 programs passing "char"s to << when the programs are compiled with C++ 2.0? ------------------------------------------------ Morris M. Keesan mmk@d62iwa.mitre.org