floor

(floor number &optional divisor)

Rounds number (or number/divisor when a divisor is given) toward negative infinity to an integer. In an ordinary (single-value) context the result is the quotient only; the remainder is the second value, observable through multiple-value-bind and the other multiple-value consumers. The function object #'floor takes the same optional divisor and answers the same two values. A NaN or an infinity as number (or a NaN divisor) has no integer to round to and signals an error; a zero divisor, exact or float, signals division-by-zero ((floor 7.5 0.0)). The same holds for ceiling, round, truncate and each f variant.