Nope, it's still an index, after the comparison and before executing the code inside the loop, i is decreased by 1. Remember that a for loop does something lik

Nope, it's still an index, after the comparison and before executing the code inside the loop, i is decreased by 1. Remember that a for loop does something like this behind the scenes: size_t i = x.size(); while( i-- > 0 ) { // your code which needs backwards iteration here ; // do nothing because there is no third statement }