Lisp's support for numbers goes beyond automatic bignum promotion, for example (/ 1 3) gives the rational 1/3 instead of an approximation, and (sqrt -1) gives #

Lisp's support for numbers goes beyond automatic bignum promotion, for example (/ 1 3) gives the rational 1/3 instead of an approximation, and (sqrt -1) gives #C(0.0 1.0), that is, 0 + 1i.