uiop:emptyp

(uiop:emptyp x)

Returns t when x is nil or a zero-length vector (a string included), nil otherwise. UIOP's one-liner, kept verbatim from upstream:

So it answers the "nothing here" question for the two shapes an empty value takes, without deciding what a non-empty non-sequence means -- a number is simply not empty.

Backend support

Works on all four backends: it is a uiop library definition written in rontolisp itself and compiled into the program when used.