simple while loop, what is wrong here?

[enim]

i just can not figure out - too tired.

i = 0;
x = 0;
y = 0;
bool sL = 0;
while( sL ) 
        {
	while( y  >=  0 ) {
		if( x < bkSz  &&  y < bkSz ); 
        {		
			dS[*i*][*0*] = x;
			dS[*i*][*1*] = y;
			i++
	}
		y−−;
		x++;
	}
	y = x;
	x = 0;
	if( i  >=  bkSz * bkSz )
		sL = 1;
}

what is wrong here?

[Selur]

the outer while loop will never be entered since 0 <> false.
also next time use 'code'-tags if you post code

[enim]

Selur,

Do you ever run a bit slower?
I was, definitely, expecting you, but, not too fast!

[Guest34343]

Wouldn't it have been obvious single-stepping through the code?

[ndjamena]

Um, wouldn't it have been obvious just knowing it doesn't work, and glancing at it? Or is that just me?

0 <> false

Do you mean 0 == false? Or are you not referring to the Basic operator?

[deadrats]

Um, wouldn't it have been obvious just knowing it doesn't work, and glancing at it? Or is that just me?

0 <> false

Do you mean 0 == false? Or are you not referring to the Basic operator?

i actually think that since the OP is setting sL to false and the while loop is effectively being interpreted as while (false) which is always true, then the program does make it past the outer while condition.

the second loop says while y is greater than or equal to 0 evaluate the rest but then he decrements y outside of the inner while loop, so the next time y gets tested it's less than 0 and thus the inner loop is only being executed once and then the gets evaluated as false every other time.

[jagabo]

Maybe the OP thought the while() test was made after executing the loop. Which is not the case as it's written. If he want the loop to execute before the test he should use a do... while loop:

do
{
    blah...

} while( sL );

[ndjamena]

While (0 <> false)

It took me a few minutes to interpret it properly. Is that c or basic? It looks like c to me but I don't use basic.

[ndjamena]

Maybe the OP thought the while() test was made after executing the loop. Which is not the case as it's written. If he want the loop to execute before the test he should use a do... while loop:

do
{
    blah...

} while( sL );

Right, he got it all backwards

i = 0;
x = 0;
y = 0;
bool sL = 1;
while( sL ) 
        {
	while( y  >=  0 ) {
		if( x < bkSz  &&  y < bkSz ); 
        {		
			dS[*i*][*0*] = x;
			dS[*i*][*1*] = y;
			i++
	}
		y−−;
		x++;
	}
	y = x;
	x = 0;
	if( i  >=  bkSz * bkSz )
		sL = 0;
}

-Edit- That was fun.

[Guest34343]

Um, wouldn't it have been obvious just knowing it doesn't work, and glancing at it? Or is that just me?

Well sure, but the OP didn't get it. When something doesn't work as expected, and you can't see why from inspection, you turn to debugging.

[ndjamena]

- too tired.

I guess you've just got to identify what the problem actually is, and fix it.

[Selur]

Do you mean 0 == false? Or are you not referring to the Basic operator?

What I wanted to indicate with me posting '0 <> false' was that '0' is equivalent to 'false' and since 'sL' was set to '0' before the while-loop and then taken as the condition for the while loop, the loop is never entered.

Sometimes it needs someone else to look at the code, even if you know the line where the bug is, you sometimes simply don't the problem since you already looked at code for too long.

[deadrats]

What I wanted to indicate with me posting '0 <> false' was that '0' is equivalent to 'false' and since 'sL' was set to '0' before the while-loop and then taken as the condition for the while loop, the loop is never entered.

actually the loop is entered, sL is set to 0 and then tested in the while conditional, but the while statement becomes while (false) which is always the case since he set it to false just prior to the loop, so the program proceeds past the outer loop and into the inner loop.

think about it for a while, if the test was while (0), the end result is that it's always zero and thus it always gets executed.

[jagabo]

What I wanted to indicate with me posting '0 <> false' was that '0' is equivalent to 'false' and since 'sL' was set to '0' before the while-loop and then taken as the condition for the while loop, the loop is never entered.

actually the loop is entered, sL is set to 0 and then tested in the while conditional, but the while statement becomes while (false) which is always the case since he set it to false just prior to the loop, so the program proceeds past the outer loop and into the inner loop.

In the OP's original post nothing inside the outer while loop is ever executed. Zero is the definition of false. So the test condition is always evaluated as false. The OP's original code is equivalent to:

i = 0;
x = 0;
y = 0;
bool sL = 0;

In fact, a good optimizing compiler would reduce it down to that (maybe less, depending on what follows).

think about it for a while, if the test was while (0), the end result is that it's always zero and thus it always gets executed.

No, it's not executed. Try it. The opposite, while(1), creates an endless loop (in the absence of a break inside the loop).

[Selur]

actually the loop is entered, sL is set to 0 and then tested in the while conditional, but the while statement becomes while (false) which is always the case since he set it to false just prior to the loop.

a while-loop (while(condition) {TODO}) is only executed if the condition evaluates to true, whether the condition changed or not is of no concern and since 0 is equivalent to false (and thus evaluates to false) the loop is never executed.

[enim]

Thanks everybody for inputs. In fact, Selur's very quick and very first response was very helpful.
I was too tired b'coz grabbing a beer was out of reach that time.
Lately got too busy on absolutely different things.

[ndjamena]

Um...

while(i  <  bkSz * bkSz )

You could save yourself a variable.

or if you need to enter at least once start with 'do'

-Edit-

if ( i  >=  bkSz * bkSz )
           break;

[ndjamena]

simple while loop, what is wrong here?

The semi-colon after the if statement should be after the i++ instead...