The right-hand side of that == is a vector containing [0, 1, 2, 3, ... 99]
The == is comparing the current value of the scalar in i to the entire vector. As i only has a single value in it, there can be at most one value in the integer range 0 to 99 that i is equal to, so the result of the comparison is either a vector of 100 false values or else is a vector that has 99 false values and one true value somewhere in it.
When you have an if statement that is testing a vector, MATLAB interprets the test as being true only if all the values being tested are non-zero. So the test is equivalent to
but we can guarantee that at the very least one value is going to be false, so we can be sure that the test will fail.
If you had written:
then that could potentially work. It would not be the recommended way to write such code, but it could work.
Better would be:
but you could also take advantage of the fact that i is never negative to code
