Article View: net.lang.c++
Article #342Overloading operators on classes' ops
From: Joseph S. D. Yao
Date: Fri, 10 Oct 1986 15:55
Date: Fri, 10 Oct 1986 15:55
42 lines
2255 bytes
2255 bytes
I tried to do something that I thought would work in C++. I think
I understand why it didn't work in C++ the implementation, but am
wondering whether I had it right in C++ the language.
Theoretically, one should be able to overload an operator with a
different routine for different type arguments. Char and int should
be different types, despite automatic promotion of constants and
function and operator arguments, right?
[Please forgive format-for-brevity in the following.]
#include <stream.h>
main(){ char ch = 'z'; cout << ch << "\n"; }
prints 122, of course, as the manual and comments say it should.
Adding AFTER this:
ostream &operator<<(ostream &s, char c) {
static char str[2] = "\0"; *str = c; return(s << str); }
gives NO CHANGE in function, and NO error message. Well, of course,
the C++ compiler hasn't seen the new overloaded operator yet. BUT
when I move the above function before main(), I get:
<< defined both as operator <<() and ostream::operartor <<()
which is supposed to be legal! (unless the args' types are the same.)
I am assuming that the implementation is treating chars as ints; but
I think I should be able to do this in the language. Comments?
By the way: ostream's operator << is defined for:
const char *, int, long, double, const streambuf &,
const whitespace &, const common &;
but note that istream's >> operator is defined for:
char *, char &, short &, int &, long &, float &, double &,
streambuf &, whitespece &, common &;
so it appears here that char is not being confused with int!
--
Joe Yao hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}
jsdy@hadron.COM (not yet domainised)
Technical Details
Message-ID:
<594@hadron.UUCP>Path:
arc1-ca.pugleaf.net!utzoo!mnetor!seismo!sundc!netxcom!hadron!jsdyShow Full Headers
Complete Article Headers
Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!seismo!sundc!netxcom!hadron!jsdy From: jsdy@hadron.UUCP (Joseph S. D. Yao) Newsgroups: net.lang.c++ Subject: Overloading operators on classes' ops Message-ID: <594@hadron.UUCP> Date: Fri, 10-Oct-86 11:55:12 EDT Article-I.D.: hadron.594 Posted: Fri Oct 10 11:55:12 1986 Date-Received: Sat, 11-Oct-86 20:02:44 EDT Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao) Organization: Hadron, Inc., Fairfax, VA Lines: 42 Keywords: char vs. int, overload, operators, << Summary: My confusion