I stopped doing this once 64 bits became a thing. There's nothing wrong per se with having your indexes signed, if you don't mind potentially not being able to

I stopped doing this once 64 bits became a thing. There's nothing wrong per se with having your indexes signed, if you don't mind potentially not being able to access the entire array - though I'm not convinced using int is very forward-thinking, as they're fairly reliably still 32 bits - but there's everything wrong with casting size_t to int. For example, assuming 64 bit, suppose i is 0x1000 and container.size() is 0x100000fff. Now (int)container.size() is very likely to be 0xfff, meaning i is greater, and something goes wrong. Or - and this would be very likely true for 32 bit systems as well - suppose container.size() is 0x80000000. Now (int)container.size() is -2147483648, meaning i is greater, and something goes wrong again. A better option would be (assuming size_t is at least as wide as int, which is vanishingly unlikely not to be true on modern systems, and can anyway be checked for using a static assert) i>=0&&(size_t)i<container.size(). Then you know the cast won't produce nonsense.