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From: richw@ada-uts.UUCP
Newsgroups: net.lang.c
Subject: Loop "Equivalencies"
Message-ID: <10200026@ada-uts.UUCP>
Date: Wed, 13-Nov-85 10:40:00 EST
Article-I.D.: ada-uts.10200026
Posted: Wed Nov 13 10:40:00 1985
Date-Received: Wed, 20-Nov-85 07:48:27 EST
Lines: 32
Nf-ID: #N:ada-uts:10200026:000:908
Nf-From: ada-uts!richw    Nov 13 10:40:00 1985


I'd like to point out what I think is a bug in Kernighan & Ritchie.
My version's copyright is 1978; please excuse this if I have an old
version and newer versions (?) have fixed it.

In Appendix A (C Reference Manual), p. 202, and p. 56, it says that
the following:

    for (expr1; expr2; expr3)
        statement

is equivalent to:

    expr1;
    while (expr2) {
        statement
        expr3;
    }

This is not true if "statement" is a block which contains a "continue"
since, in the first case, "expr3", is executed after the continue but
is not in the second case.

I came across this while working on someone else's code.  This code
constantly used the "while" form in places where I thought a "for"
was more concise and appropriate.  So, whenever I'd see the second
"while" form, I'd transform it (based on this buggy K&R statement).
Then I got burned...

Am I missing something?

-- Rich Wagner