the library uses a fairly simple data representation where x{m,n} is compiled using conjunction and disjunction. so x{1,4} ends up being represented as x|xx|xxx|xxxx.

this simplifies the code for testing equality and inclusion, since logically x{n} is just xx... (n times) and x{m,n} is just x{m}|x{m+1}|...|x{n}.

but when you have x{m,n} and n-m is large you can imagine what kind of problems that causes.