c++: coma operator

I use coma operator all the time:

int a, b;
for (a=1,b=1;a<3;++a,++b)
    ...

Probably some other cases. By specification coma operator allows to call a sequence of instructions where one is allowed. So

true?(++a,b+=2,a+b):(a+=2,++b,a-b)

will evaluate ++a,b+=2 and return a+b. The other awesome thing with coma that it breaks rule for necessity of braces for blocks of code. Multiply instruction can be folded into one:

if (a == b)
    a=1, cout << a+b;