#defineQuestions !!!

xqrhrh

#define CHR (r) r * r

main ()
{
  printf ("% d", CHR (1 + 2));
}

what's the result. Let me try. The result is 5. Why is it 5. What is the mechanism?

wogenius

What's wrong with this person?

I like to drill horns ...

This kind of problem has been discussed N times ... makes no sense.

#define CHR (r) (r) * (r)

xqrhrh

Exam to take this question

xqrhrh

#define CHR (r) (r) * (r)

If you said (r) * (r)

Then CHR (2 + 3) should be equal to 4 + 9 = 13

Possible result is equal to 11

wogenius

Is 1 + 2 * 1 + 2 = 5

wogenius

Macros are replacements.

Without parentheses, a result equal to 5 will appear.

sing2002

Let me also add:
If you want insurance, I think it should be like this:
#define CHR (r) ((r) * (r)),
Add a parenthesis to the outermost layer, hehe, otherwise, if there is such an expression:

CHR (r1) / CHR (r2),

#define CHR (r) (r) * (r), there may be some problems.