Path: utzoo!attcan!uunet!convex!graham
From: graham@convex.com (Marv Graham)
Newsgroups: comp.lang.c++
Subject: Re: FORever
Message-ID: <106731@convex.convex.com>
Date: 1 Oct 90 19:30:06 GMT
References: <1990Sep27.150948.9109@sco.COM>
Sender: usenet@convex.com
Organization: Convex Computer Corporation; Richardson, TX
Lines: 60

In article <1990Sep27.150948.9109@sco.COM> ron@sco.COM (Ron Irvine) writes:
>
>BEWARE there is a major problem with C++'s "for" statement.
>
>main() {
>	for (int i=10; i<13;) {
>		for (int i=0; i<3; ++i)
>			; // stuff
>		++i;
>	}
>}
>
>Cfront accepts this code and compiles without warning.
>The resulting code is totally unexpected!
>The program loops forever?!!
>
>I realize the problem is that cfront does not end the
>scope of the inners loop's "i" until the end of the
>outer loop, thus the "++i;" statement actually increments
>the inner loops "i" whos scope is the outer loop.  And I
>did not "redeclare" "i" in the outer loop since the outer
>"i"'s scope is outside the outer loop.
>
>This is a bad joke for a language that is designed for the 90's.
>The scope of a variable in a "for-init-statement" MUST end
>at the end of the "for" statement. Lets change the definition of
>the language NOW before we inflict horrendous pain on C++ programmers.

In my opinion, the PROBLEM is using a badly defined new toy instead
of writing

main() { int i ;	// this really belongs here
	for (i=10; i<13;) {
	    {	// this really is needed here
		int	i ;	// and this really belongs here
		for (i=0; i<3; ++i)
			; // stuff
	    }	// this makes the next ++i refer to the outer one
		++i;
	}
}

If you say what you mean, you get what you want.

What we should really do is make the nested definitions illegal (again)!

But, if you had just a little common sense, you would write

main() { int	i ;
	for (i=10; i<13;) {
		int	j ;	// what, not "i" again??
		for (j=0; j<3; ++j)
			; // stuff
		++i;
	}
}

Can't you really think of a name for a for loop index besides "i"?

Marv Graham; Convex Computer Corp.  {uunet,sun,uiucdcs,allegra}!convex!graham