Except that it allows for an arbitrary modulus. For instance, you can have:
type Whatever_Name is mod 10;
Removing restrictions is nice, lets the language and its type system actually express parts of the program logic unlike the inexpressive type system C provides.
No. Dependent types go further and allow you to do things like express that the length of an output vector/array is the same as some input number. That is, depends on some value (as in a runtime value). This mod type is fixed at compile time.
