On 7/8/11 Fri Jul 8, 2011 4:33 PM, "J. S. John" <phillyj...@gmail.com>
scribbled:
> Hi all,
> I'm teaching myself perl. Right now, I am stuck with this script. I
> don't understand how it works. I know what it does and how to do it by
> hand.
>
> $n = 1;
> while ($n < 10) {
> $sum += $n;
> $n += 2;
> }
> print "The sum is $sum.\n"
>
> I know $sum is initially 0 (undef). I see that $sum becomes 1, then $n
> becomes 3. The loop goes back and then I don't understand. Now $sum is
> 1+3?
Yes.
The while loop will repeat as long as its conditional expression is true. In
this case, it will loop as long as $n is less than 10. Since $n is 1 at the
beginning of the loop and incremented by 2 during each iteration of the
loop, $n will have the successive values 1, 3, 5, 7, and 9 during 5 loop
iterations. At the beginning of the 6th iteration, $n has the value 11.
Since the logical expression '$n < 10' is now false, the loop body is
skipped, and execution resumes at the first line after the loop body (the
print statement).
At the end of the loop, $sum should have the value 1 + 3 + 5 + 7 + 9, or 25.
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