From 4076412111181604480 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,67a6649d91bbc903 X-Google-Attributes: gidf78e5,public X-Google-Thread: 109fba,67a6649d91bbc903 X-Google-Attributes: gid109fba,public From: ajoycs@netscape.net Subject: Re: Operator overloading question Date: 1998/10/28 Message-ID: <7179pg$7as$1@nnrp1.dejanews.com>#1/1 X-Deja-AN: 406016363 X-NNTP-Posting-Host: 164.100.9.113 Approved: stephen.clamage@sun.com (comp.std.c++) References: <7138et$mrk$1@nnrp1.dejanews.com> <7155ks$94u@crcnis3.unl.edu> X-UID: 0000000001 X-Status: $$$T X-Http-User-Agent: Mozilla/4.5 [en] (X11; I; SunOS 5.5.1 sun4u) X-Http-Proxy: 1.0 x4.dejanews.com:80 (Squid/1.1.22) for client 164.100.9.113 Organization: Deja News - The Leader in Internet Discussion X-Article-Creation-Date: Wed Oct 28 14:30:08 1998 GMT Newsgroups: comp.lang.c++,comp.std.c++ Originator: clamage@taumet Hi: Does what you have look like the following?? class String { //... public: //... char& operator[]( int index ) { /* ... */ } char operator[]( int index ) { /* ... */ } }; This should be *rejected* by the compiler....(according to me :) Even if the compiler did'nt crib ... how would you tell the compiler which operator[] _you_had_in_mind_ when you wrote say, myString[x] somewhere.?? It most probably must be taking the first definition of operator[] when it doesnt want to trouble you. This is dangerous though!!! If you want myString[x] to appear on the lhs of an assignment stmt you should probably always return a reference. But the need for return-by-val is a legit one. meaning ... it return a l-value only when used as a lhs of an assignment operator and return a value in all other cases(like func.args etc..). But then I feel this prob cant be solved by an operator[] always returning a ref&. To me this looks like some design issue... More discussion may be needed here. All suggestions/comments welcome from the "experts". Ajoy CS. In article <7155ks$94u@crcnis3.unl.edu>, "Jeff" wrote: > rama_srinivas@hotmail.com wrote: > > >Hi, I am writing a String class which does bounds-checking and dynmaic > >resizing of the array. I want to overload the indexing operator([]) in the > >following manners: char & operator[](int index); char operator[](int > >index); One of them - the first one - returns a reference so that the > >l-value usage is checked for bounds-overflow(or underflow). The second > >variant returns a char value which can be assigned to another l-value or > >passed to functions expecting char value as input(like tolower() etc.,). How > >ever, the signature of both the functions is the same and this does not > >compile under VC++. Surprisingly, this compiles fines on a HP system and > >works too - though I have to check which function is being called in which > >case. I cannot write different code for Unix/NT since the code base is to be > >the same. Is there any way that this can be done in C++? If yes, how? > > For once VC is correct. You cannot overload a function (an operator is just a > special function) by return type. I'm not sure what the HP compiler is up to, > but I'm guessing that for some reason it's ignoring one of the two definitions. > Since it works correctly, I'd say it's using the return-by-reference version. > > I'm a little confused as to what the difference between the two operators is. > You have char& operator[](), which does a range check and and returns the > reference so that you can assign to it. Then you have char operator[](), which > _should_ be range-checked, and returns the value of the char. The way I see it, > there is no need for the second version. Use the first operator to do a range > check and then return a reference to the appropriate character. You can either > assign to or read from that reference, and the need for the return-by-value > version is eliminated. > > -Jeff -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]