Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!umich!samsung!sol.ctr.columbia.edu!emory!hubcap!ncrcae!PEDEV!rogerson
From: rogerson@PEDEV.Columbia.NCR.COM (Dale Rogerson)
Newsgroups: comp.lang.c++
Subject: Re: Passing by reference (was Re: C++ coding standards (Comment needed))
Keywords: standard,variables
Message-ID: <3233@PEDEV.Columbia.NCR.COM>
Date: 23 Aug 90 19:56:13 GMT
References: <2161@runxtsa.runx.oz.au> <183@logo.procase.UUCP> <15361@reed.UUCP>
Reply-To: rogerson@PEDEV.Columbia.NCR.COM (Dale Rogerson)
Organization: NCR Corp., Engineering & Manufacturing - Columbia, SC
Lines: 43

In article <15361@reed.UUCP> minar@reed.bitnet (Nelson Minar) writes:
>However, I find it really nice to know in C that 'hey, in this function call
>that variable is passed by value. The function can't be changing the value
>of that variable, and thus the bug is elsewhere.'  Its useful when debugging
>other's arcane code.

>In C++, this information is not available merely from the function call.
>Who knows if
>	int a = 0;
>	foo(a);
>will change the value of a or not in C++, without finding the prototype for
>the function and looking carefully.

>Is there any sort of nice convention to make this easier to deal with? I assume
>not.

Modula-2 (and Pascal) have always had passing by reference just specify the
parameter as VAR (i.e. foo( VAR a ) ).  I have never found this to be a 
problem in Modula-2.  However, Modula-2 has a very well defined idea of a
module.  Each module must have a Definition file and an Implementation file.
It is really easy to find out which file a function call is in and a quick
look at the Definition file will tell you what it modifies.  It is very 
quick and painless.  I have never been bitten by this, but I have been 
bitten by the missing & operator in C.

If you have well chosen filenames and classnames and provide good header 
files this should not be too bad in C++.  Remember that most(?) function calls
will probably be through a class pointer so finding the class should be
easy.  A nice solution would be to adopt the Modula-2 idea of Definition
and Implementation files which would cure many of the header file problems.
However, most C programmers are already accepting a suprising amount of 
Modula-2 ideas so I probably better not push my luck. :-)

The best solution is probably to get a good code browser which would get you
the function prototype at the press of a key. This requires no changes to
the language definition.  It might require coding practice changes.

None of these solutions will help for arcane code.



-----Dale
	Rogerson-----