What would be different about loop variables? I don't really write C++.

I'm assuming here that they would use the `size_type` for the container they are iterating over. Otherwise I'm not sure.

An unsigned type is sometimes a poor choice for a loop index. The compiler then cannot assume the loop will terminate, and generate worse code. Usually this doesn't matter -- until you discover it did.

Good point. Probably not a problem in practice for most containers, but yet another reason for why the STL (and C library, for that matter) should have used a signed size type from the beginning.

Yep, it's to match vector/array size_type and difference_type, although I tend to just use size_t and ptrdiff_t directly.

It's a good choice. Sometimes your best choice for a general purpose int is

    typedef Int int32_t;

for the entire compilation as a whole, and when things get screwy just bump Int up to int64_t and take the performance hit for the extra bit of safety

"i32" is better.