i was given the code:

#include <stdio.h>
int main(void) {
    int a = 0, b = 0, c = 0;
    c = (a -= a - 5), (a = b, b + 3);
    printf("a = %d, b = %d, c = %d", a, b, c); // a = 0, b = 0, c = 5
}

and my task was to figure out how it works. i do not understand how the line

c = (a -= a - 5), (a = b, b + 3); 

works, though.

my guess is that it works just like this code:

#include <stdio.h>

int main(void) {
    int a = 0, b = 0, c = 0;
    a -= a - 5;
    c = a;
    a = b;
    b + 3;
    printf("a = %d, b = %d, c = %d", a, b, c); //a = 0, b = 0, c = 5
}

because the result is the same.

but i don’t understand the first version of the code. so firstly, in changes the value of a (a becomes 5), then changes the value of c (c becomes a), and then in performs the expression in the second parantheses (which seems to not affect the value of c at all, although it’s the same line of code and there was no semicolon in between, only a comma. what is that syntax? is there a name for that kind of syntax? i just don’t understand why it was written like that and why it does what it does.

also, less importantly, what does the line

b + 3;

do? is it just nothing?..