I have the following program, which should be simple to everyone but me!
#include <iostream>
using namespace std;
int main()
{
int a, b;
b = 1;
cout << ((a = --b) ? b : (b = -99)) << '\n' << "a is " << a << '\n' << "b is " << b << endl;
b = 1;
cout << (a = --b ? b : (b = -99)) << '\n' << "a is " << a << '\n' << "b is " << b << endl;
}
The output of the program is:
-99
a is 0
b is -99
-99
a is -99
b is -99
On the first segment of code what I understand is that a is given the value --b, 0, so it becomes false, so b=-99 is executed. I can't understand the second segment of code, where a=--b has no parentheses, why a is given the value -99.
(a = --b ? b : (b = -99))
here, because = and ? have the same priority (15 according to the link provided) and are evaluated from right to left, it is executed as follows:
a = --b ? b : (b = -99)
1. --b ( =0)
2. 0?
3. 0 so not what is immediately after ? but what is after :
4. b=-99 (evaluate second expression)
5. a = -99 (assign the result of expression)