Question

How to analyze these two following lines of code?

w += /* 28 + */ y % 4 == 0 && (y % 100 || y % 400 ==0);

and

 w += 30 + (i % 2 ^ i >= 8);

Answer 1

Here is how to analyze it

int main(){
    int w = 0;
    int y = 400;

    w += /* 28 + */ y % 4 == 0 && (y % 100 || y % 400 ==0); 

    int t1 = y % 100;
    int t2 = y % 400;
    
    int t3 = t1 | t2;

    bool t4 = (y % 4);

    int w1 = t3 & t4;
}

Note that t1 and t2, can be evaluated in any order
t3 will be evaluated after t1 and t2
t4 can be evaluated before either t1 or t2

This requires familiarity with

operator associativity

operator precedence

sequence points

Leaving the other one also to be analyzed on similar lines