micro in c

govindasahu · 08-22-2011, 09:51 AM

#define test(a) a*a
void main()
{
int i=3;
printf("%d",test(i+4));
}

ans is : 19
how?????????

dugan · 08-22-2011, 10:07 AM

You can't work it out yourself?

i = 3
test(a) = a * a
test(i + 4) = i + 4 * i + 4 // note the lack of brackets!
test(i + 4) = 3 + 4 * 3 + 4
test(i + 4) = 19

What you wanted to write was this:

Code:

#define test(a) (a*a)

Nylex · 08-22-2011, 10:08 AM

Look at the output after preprocessing (with gcc, you can use the -E option):

printf("%d\n", i + 4 * i + 4);

Is there any reason you need to use a macro rather than a function?

Edit: Damn you, dugan!

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