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From: "Jerry Coffin" <jcoffin@taeus.com>
Newsgroups: comp.lang.ada,comp.lang.c++
Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
Date: 23 Mar 2005 19:33:19 -0800
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Date: 2005-03-23T19:33:19-08:00
List-Id: <comp.lang.ada>

Jim Rogers wrote:

[ ... ]

> For instance the following macro can cause some serious problems when
> mis-applied:
>
> #define SWAP(A,B)  ((temp) = (A);(A) = (B); (B) = (temp))
>
> char s1[30];
> int i;
>
> SWAP(S1, i);
>
> In many cases it is safer to define an in-line function than to
> define a macro.

I don't see a particularly serious problem here -- the code simply
won't compile. At the moment you have some syntactical problems and
sloppiness that's overlooked by Ada comilers (because Ada is
case-insensitive).

Even ignoring those, however, it will fail because of a
type-difference. To give a concrete example, after (partially) fixing
your code above, Visual C++ says:

swap.cpp(7) : error C2440: '=' : cannot convert from 'int' to 'char
[30]'
        There are no conversions to array types, although there are
        conversions to references or pointers to arrays

Modulo trivial things like ':=' vs. '=', 'int' vs. 'Integer', etc., I
suspect that's on the same general order as you'd expect to see from an
Ada compiler given code that attempted to assign an Integer to an array
of characters.

I think most C++ programmers, however, would tend to agree that in this
case you'd generally be better off using std::swap.

--
    Later,
    Jerry.

The universe is a figment of its own imagination.