output of #define

[incognito]

I have a micro defined

#define multi(a,b) a*b 

now what would be the output when I say
multi(2+2,3+3) ? My compiler gives output as 11. But I don't understand how it is doing it. Could somebody please explain?

Some random outputs are
multi(1+2,3+5) // 12
multi(4+4,3+3) //19

Not getting the logic behind it :( Thanks in advance.

[Peter87]

The preprocessor doesn't care about C++ syntax. When it sees multi(2+2,3+3) it will just replace it with 2+2*3+3.

[Caligulaminus]

#define multi(a,b) a*b

multi(2+2,3+3) ==> 2+2*3+3 == 11

#define multi(a,b) (a)*(b)

multi(2+2,3+3) ==> (2+2)*(3+3) == 24

[Disch]

This is reason #63 why you should avoid macros.

use an inline function instead:

int multi(int a,int b) { return a*b; }

or if you want to be fancy:

template<typename T>
T multi(const T& a,const T& b) { return a*b; }

[Peter87]

.. if you want to be even more fancy:

template<typename T1, typename T2>
auto multi(const T1& a,const T2& b) -> decltype(a*b) { return a*b; }

[incognito]

Oops..right. Compiler doesn't care about syntax..How did I miss this thing :( Thanks a lot for help.
(I hate using macros, but this was a question asked to me in interview and I was looking at it like a fool for 10 mins..Wondering what the hell!) :D