Simple Stupid If Question
Author
What is the default condition in this IF?
LPDIRECTDRAWSURFACE7 extractor = NULL;
if (extractor)
{
extractor->Release();
extractor = NULL;
}
Is it if TRUE or not NULL?
Fud
If you'd actually looked at how NULL was defined, you'd see it was 0.
That means that if statement is:
If extractor was NULL, then it'd be NULL != NULL, which is false, but if it's not NULL, then it'd be <some memory address> != NULL, which would hold true.
That means that if statement is:
if (extractor != NULL)If extractor was NULL, then it'd be NULL != NULL, which is false, but if it's not NULL, then it'd be <some memory address> != NULL, which would hold true.
Author
Erm.....
Well I'm not sure if I'm more confused wit that answer.
I guess all I wanted to know was the condition.
if "if (extractor)" is the same as "if (extractor !=NULL)" just written different?
Thanks
Fud
Well I'm not sure if I'm more confused wit that answer.
I guess all I wanted to know was the condition.
if "if (extractor)" is the same as "if (extractor !=NULL)" just written different?
Thanks
Fud
Quote:Original post by LMRFUD
What is the default condition in this IF?
LPDIRECTDRAWSURFACE7 extractor = NULL;
if (extractor)
{
extractor->Release();
extractor = NULL;
}
Is it if TRUE or not NULL?
Fud
In your case variable, 'extractor' is NULL or 0 so that would mean your if statement evaluates to 'false'. Your if statement could be written as :
if( extractor )if( extractor != 0 )if( !(extractor == 0) )if( extractor != NULL )if( !(extractor == NULL) )
Well, I guess you've already figured this out, but true means a positive number, ie. above 0. Everything that is 0 or below is counted as false.
Quote:Original post by nife
Well, I guess you've already figured this out, but true means a positive number, ie. above 0. Everything that is 0 or below is counted as false.
Wrong! False is always zero. True is anything but zero.
Quote:Original post by Anonymous PosterQuote:Original post by nife
Well, I guess you've already figured this out, but true means a positive number, ie. above 0. Everything that is 0 or below is counted as false.
Wrong! False is always zero. True is anything but zero.
TRUE STORY
(that means he[AP] is correct)
Just a suggestion, but never type (var == number) since leaving out the second equal will cause var to be assigned the value in number.
Instead, always write (number == var). That way, leaving out the second = will cause a compile time error, not a run time error
// don't do thisif(var == NULL)...// if you leav out the second =, then var will be set to zeroif(var = NULL)...// oops, var is equal to null now!Instead, always write (number == var). That way, leaving out the second = will cause a compile time error, not a run time error
// do it this wayif(NULL == var)...
If you're going to offer advice you should probably give a better explanation why. You didn't mention constants at all!
Constants cannot be on the left hand side of an assignment, but they can be on the left hand side of a comparison. So if you always put the constant to the left of a comparision and you accidently forget the second equal sign you will get an error when you compile saying you can't assign something to a constant. You will look at the code and think, "hey! there should be another equals sign"
Constants cannot be on the left hand side of an assignment, but they can be on the left hand side of a comparison. So if you always put the constant to the left of a comparision and you accidently forget the second equal sign you will get an error when you compile saying you can't assign something to a constant. You will look at the code and think, "hey! there should be another equals sign"
This topic is closed to new replies.
Advertisement
Popular Topics
Advertisement
