for (int i = 1; i <= 10; i++)
cout << i << endl;
I expected the following:
1
2
3
4
5
6
7
8
9
10
11
When it comes to the last iteration i is 10.
Then i++ increments, but returns the old value 10.
So, condition is again true.
Now, i in the body of if is 11.
Apparently, I am wrong.
Does the postfix increment operator function differently within a for
construct? 11 2006
Roman Töngi wrote: for (int i = 1; i <= 10; i++)
The above can also be written:
for(int i=1; i<11; i++)
cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
In both cases the loop body is executed for i values in [1, 10].
--
Ioannis Vranos http://www23.brinkster.com/noicys
Roman Töngi schrieb: for (int i = 1; i <= 10; i++) cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
No.
Maybe it get's clearer if you re-write the for-loop as a while-loop
(which are semantically equivalent, except for the scope of the loop
variable i):
int i=1;
while(i<=10)
{
cout << i << endl;
i++;
}
HTH
Stefan
Roman Töngi schrieb: for (int i = 1; i <= 10; i++) cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
No.
Maybe it get's clearer if you re-write the for-loop as a while-loop
(which are semantically equivalent, except for the scope of the loop
variable i):
int i=1;
while(i<=10)
{
cout << i << endl;
i++;
}
HTH
Stefan
"Roman Töngi" <ro**********@bluewin.ch> wrote in message
news:42**********@news.bluewin.ch When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
No, but the return value from incrementing is not of interest. It
used nowhere in the code. First, you increment, then you use i to check
the condition. Note: you do not use the return value, but the new value
i has.
hth
--
jb
(reply address in rot13, unscramble first)
> for (int i = 1; i <= 10; i++) cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
The two expressions i<=19 and i++ are evaluated independently, so when i is
incremented from 10 to 11, then 11 is stored and used for the comparison.
Niels Dybdahl
I understand. Condition and Expression within the if head
are separate.
Thanks
On Wed, 20 Apr 2005 08:33:01 +0200, Roman Töngi <ro**********@bluewin.ch>
wrote: for (int i = 1; i <= 10; i++) cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
i would say that the postfix increments i after the whole loop is done. so
when the loop has printed 10, i is incremented to 11, _then_ the loop
condition is evaluated and the loop isn't entered any more. so, no
printing of 11.
:)
"ulrich" <ua********@aon.at> wrote in message
news:opspisc6sin2mgp5@innsbruck-neu... On Wed, 20 Apr 2005 08:33:01 +0200, Roman Tvngi <ro**********@bluewin.ch> wrote:
for (int i = 1; i <= 10; i++) cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a for construct?
i would say that the postfix increments i after the whole loop is done. so when the loop has printed 10, i is incremented to 11, _then_ the loop condition is evaluated and the loop isn't entered any more. so, no printing of 11.
:)
Just to be clear... the same would happen with a prefix operator instead of
a postfix operator. The expression portion of the for statement is *always*
executed after the loop is executed.
-Howard
"Roman Tvngi" <ro**********@bluewin.ch> wrote in message
news:42**********@news.bluewin.ch... I understand. Condition and Expression within the if head are separate.
That's a "for" loop, not an "if" statement. Forget your coffee this
morning? :-)
-Howard
Howard wrote: "ulrich" <ua********@aon.at> wrote in message news:opspisc6sin2mgp5@innsbruck-neu... On Wed, 20 Apr 2005 08:33:01 +0200, Roman Tvngi
<ro**********@bluewin.ch> wrote:
for (int i = 1; i <= 10; i++) cout << i << endl;
I expected the following: 1 2 3 4 5 6 7 8 9 10 11
When it comes to the last iteration i is 10. Then i++ increments, but returns the old value 10. So, condition is again true. Now, i in the body of if is 11.
Apparently, I am wrong. Does the postfix increment operator function differently within a
for construct? i would say that the postfix increments i after the whole loop is
done. so when the loop has printed 10, i is incremented to 11, _then_ the
loop condition is evaluated and the loop isn't entered any more. so, no printing of 11.
:)
Just to be clear... the same would happen with a prefix operator
instead of a postfix operator. The expression portion of the for statement is
*always* executed after the loop is executed.
-Howard
Hi,
I'll show you the execution order of a 'for loop' then you'll
understand
for ( int i = 0; i <= 10; i++)
cout << i;
Order Of Execution;
1) i = 0 ----> i initialized
2) i <= 10 condition checked ( if evaluates to true you get in to the
loop else
you exit the loop. your i will remain as 0 if you exit here
3) if in step 2 you did not exist i++ would be evaluated
4) now onwards step 2 and 3 are followed till you exit the loop.
just after you have 10 output i would be incremented to 11 and then the
condtion checked and evaluates to false and you exit the loop without
printing
10. but your i would contain the value 11
rgds
ruksan
"ruksan" <ru****@gmail.com> wrote in message
news:11**********************@l41g2000cwc.googlegr oups.com... Hi,
I'll show you the execution order of a 'for loop' then you'll understand
for ( int i = 0; i <= 10; i++) cout << i;
Order Of Execution;
1) i = 0 ----> i initialized
2) i <= 10 condition checked ( if evaluates to true you get in to the loop else you exit the loop. your i will remain as 0 if you exit here
3) if in step 2 you did not exist i++ would be evaluated
That should read:
3) if in step 2 you did not exit the loop, then the loop body would be
executed. After that, the expression (i++, in this case) would be
evaluated. 4) now onwards step 2 and 3 are followed till you exit the loop.
just after you have 10 output i would be incremented to 11 and then the condtion checked and evaluates to false and you exit the loop without printing 10. but your i would contain the value 11
The variable i would indeed contain 11 when the check is made, but once the
loop is exited, i is no longer in scope and thus cannot be said to have any
value at all.
-Howard This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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