Thread: size_type

size_type makes sure that it can hold the largest number that corresponds to the largest data structure. size_type is an integer that can hold a number than an integer may not be able to hold. It says that in the "why size_type" part in bold in that same book not to far from where it first appears.

I was wondering how important it is to use the size_type over just an integer?

It's not really.

The reason that size_t is useful though is because it separates the placement, size, or length of items from regular numbers like ints. Also, the size of anything will never be below 0 so it makes sense to use size_t for that sort of thing.

In toy programs, it probably makes no real difference - but that doesn't mean you shouldn't get into the habit of using it. Aside from the fact that, as indigo0086 said, there's a possibility that int and size_t are not the same, self-documenting code is a very useful asset. When you begin to write larger projects spanning across several source files, typedefs such as size_t are POD types with added context - using them can make the reader's life just a little bit easier instead of the POD type itself.
Its not just for yourself either (when you return to code 6 months down the line after a break, you will inevitibly forget what certain parts of the code actually do), but for other people who you may call upon to help if you get stuck at any particular point, its even more important that they can understand what thought processes you were going through when you created your code.