How does this code of c++ gives the output??

[rahul.6sept]

Dear All,

the following code of c++ gives an output which I could not understand as how is this coming. Can someone help me understand it.

#include <iostream>
using namespace std;

#define MM_1(x,y) x*y
#define MM_2(x,y) (x*y)
#define MM_3(x,y) (x)*(y)

inline int MPLY (int x, int y){return x*y;}

int main(){
     int a=3,b=4;

     cout << "MM_1:" << MM_1(MM_1(a+1, b-1), a+b)<<endl;
     cout << "MM_2:" << MM_2(MM_2(a+1, b-1), a+b)<<endl;
     cout << "MM_3:" << MM_3(MM_3(a+1, b-1), a+b)<<endl;
     cout << "MPLY:" << MPLY(MPLY(a+1, b-1), a+b)<<endl;

     return 0;
}

I calculated for MM_1 the output to be 84 but the output it gives to be is only 8. How it is calculating it?

Regards

 

[furqankaimkhani]

hi Rahul, (Kaise ho?)

I am guessing that this Code's basic purpose is to highlight the same difference of results that you are getting. The reason of "8" in the result is the way C++ reads and performs its operations according to its precedence rules. You can read the CPP precedence rules on internet. Here is a link : "https://en.cppreference.com/w/cpp/language/operator_precedence"

Now, let me explain how it calculates 8 as the result:
for a=3, b=4

>> MM1(MM1(3+1,4-1),3+4)
>> MM1(3+1,4-1) * 3+4
>> 3+1*4-1*3+4
>> 3+4-3+4
>> 7-3+4
>>11-3
>>8

Hope it helps,
Regards,