Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!jimad
From: jimad@microsoft.UUCP (Jim ADCOCK)
Newsgroups: comp.lang.c++
Subject: Re: How many arguments for operator() and operator[]?
Keywords: overloading, operator, arguments
Message-ID: <70485@microsoft.UUCP>
Date: 5 Feb 91 19:18:32 GMT
References: <19587@shlump.nac.dec.com>
Reply-To: jimad@microsoft.UUCP (Jim ADCOCK)
Organization: Microsoft Corp., Redmond WA
Lines: 32

In article <19587@shlump.nac.dec.com> heintze.fmcsse.enet.dec.com (Sieg Heintze) writes:
>Could someone point me to the place in the Stroustrup and Ellis C++ Reference
>manual where they define the number of arguments permitted when defining
>a member function that overloads operator() or operator[].
>
>I have tried this program on three compilers and all three behave differently.
>I'm wondering how other C++ compilers behave and just what the correct
>behavour is.

See ARM page 335-337.  Overloaded operators are suppose to follow the same
syntax as built-in operators.  Thus, op[] can only have two operators --
foo[bar] has a first [implied] parameter of foo, and a second parameter
of bar.  Op[] must be a non-static member function.

The usage form of op() is:

primary-expression(optional-expression-list)

op() must also be a non-static member function.

Thus:

int X::operator()();
foo X::operator()(int x, double y);
foo X::operator()(int x);
double X::operator()(int a, int b, int c, int d, int f, double x);

should all be accepted.

ARM refers to op() as being a "binary operator" -- which might have confused
some implementors -- though ARM does give examples of op() being used with 
totals of three and four parameters.