Someone help me with this code in C++ include #using namespace std; int main () { int x=0; int y=0; if (x++ && y++) { y+=2; } cout

Question

Someone help me with this code in C++
include<iostream>
#using namespace std;
int main ()
{
int x=0;
int y=0;
if (x++ && y++)
{
y+=2;
}
cout<<x+y<<endl;
return 0;
}

Can you explain me why the sum x+y is 1 ?

konradzuse · Answer

I believe it's because you said if(x++ && y++)  That's just making x + 1, and I'm assuming it's doing nothing to y.  You should say if x == 1 and y == 1, but what exactly are you trying to accomplish with this?

rsmith6559 · Answer

x++ and y++ are post incrementing.  This means that the values of x and y are evaluated, and then x and y are incremented.  This means that your if statement evaluates to false ( 0 & 0 = 0 logical false ).  After the if, both x and y are incremented.  Therefore the cout outputs 1 + 1 = 2.

If you change " y += 2 " to " y += 3 ", it will become more apparent.

anonymous · Answer

The sum is actually output as 1.
x is 1 and y is 0.

Why?

Because of short-circuit evaluation.
Inside the if statement, the left side of the && is evaluated (x++), it returns 0, which is false, and then it increments. The left side evaluates to false and so the right side is ignored.

konradzuse · Answer

^yeah exactly, because of that if(x++ && y++) I guess I didn't explain that now that I look back at what I said.  ++i should return 1.  ++i returns right away, while i++ returns after the for loop I believe...

anonymous · Answer

Thank you :) Actually this was an exercise that my teacher gave us in the midterm.We have one month learning c++,and we are begginers so we have just learnt a few simple things ,and this exercise was very confused for us.