I can't speak for Erlang's internals, but Lisp is one of if not the earliest implementer of this concept. It internally separates the integer space into "fixnu

I can't speak for Erlang's internals, but Lisp is one of if not the earliest implementer of this concept. It internally separates the integer space into "fixnums" and "bignums". Fixnums are around register-width and use the plain ol' machine math instructions. Operations which are inferred or declared to stay within fixnum range don't even have bignum calls compiled into them.