[iMacfan]

Hi,

I'm trying to program my palm in C, but it doesn't want to do a for loop inside an if statement:

int x = 0;

if(x = 0)
{
for(i=1 ; i<=30000 ; i++)
{
SndDoCmd(NULL, &snd, 0);
SysTaskDelay( delay );
if(EvtSysEventAvail(true))
{i=30000;}
}
}


Without the if(x=0){}, everything works fine.

Thanks for any help,

David

[Chuckit]

The problem isn't putting the for-statement inside. The problem is you miswrote your if-statement.

x = 0 means "assign the value 0 to the variable x"
x == 0 means "check if x is equal to zero, and if so, yield a non-zero result"

You should be using the second one in your if-statement, but you are using the first. The expression "x = 0" evaluates to 0, so whatever is inside it will never get executed.

[iMacfan]

Thank you so much!

I guess it's the sort of thing that you just don't see if you wrote it yourself.

I can assure you that there is much slapping of foreheads here!

David

[Chuckit]

Yep. It's an easy mistake to miss. That's the reason why many programmers make it a point to put constants first:

if (0 == x)
if (nil == passedObject)

Because you can't assign to constants, so if you accidentally miss an equals sign, the compiler will recognize that you've made a mistake.

[iMacfan]

Excellent idea - I was wondering why the compiler did not pick up my stupid mistake.

David

[Richard Edgar]

I was wondering why the compiler did not pick up my stupid mistake

Because it's not a mistake. In C it is perfectly legal to do something like

Code:
if( x = 0 )
{
...
}

and a variety of similar things. However, I think most compilers will have an option somewhere to issue warnings when such things are tried. Check the documentation.

[Chuckit]

Like I said, if() just checks whether the expression in the parentheses evaluates to a non-zero value, and if so executes the associated block of code. So if you write if (x = 0), you have entered a valid C statement that always evaluates to 0.