Problem with ()?():() as ending test in for-loop

[Gary L. Randolph]

In article <20658 at news.Think.COM> barmar at kulla.think.com.UUCP (Barry Margolin) writes:
>In article <1200 at liszt.kulesat.uucp> vanpetegem at liszt.kulesat.uucp writes:
>>The code with which I am in trouble, goes as follows:
>>
>>	 for(n = 1;  ((n % 10) ? (k > 2) : (n < 100));  n++)
>>                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>           {
>>             ..... (in some expressions k is changed, depending on n)
>>	   }
>>What I want to do is simply perform the test (k > 2) as ending test for the
>>"for-loop", except in the cases where n is dividable by 10. In the latter
>>situation the test (n < 100) has to be done.

=The sense of the test clause of your :? expression is wrong.  When n
=is divisible by 10, (n % 10) is 0, and 0 represents "false" in C.  I
=would write your end test as
=	((n % 10) == 0) ? (k > 2) : (n < 100)
=i.e. they would just interchange the true and false clauses, taking
=advantage of the fact that the result of the % can be used as a
=boolean.

NOOOOO! I do NOT think your logic is wrong.  I am sure it is correct
according to  your explanation of what you want to do.  There *is* a
problem however...

The modulus operator, when used for integer division as in your 
example, truncates the fractional part.  This, of course, makes the
initial check result in a fall out of the for since 1%10 *is* 0 and
therefor the n<100 test is done and, n being 1 bye-bye.

This, I believe is your real problem. Also, you don't mention whether
variable k was initialized before entering the for.  IT SHOULD BE.

I hope this helps...

                           --Gary Randolph