Arbitrary precision integers aren't necessarily that expensive to implement. It does require overflow checking for operations on regular fixed integers, and ke

Arbitrary precision integers aren't necessarily that expensive to implement. It does require overflow checking for operations on regular fixed integers, and keeping track of type, but if you're doing that anyway (many languages are) then it's almost free; the bignum code only runs when it doesn't fit in a fixed integer. Common Lisp, Python, Haskell use big integers for all integers, too. And others, I'm sure. It can be optimized away by a compiler to just fixed integers, sometimes.