uiop:absolute-pathname-p

(uiop:absolute-pathname-p pathspec)

The parsed PATHNAME when pathspec is absolute (a generalized boolean, as upstream), nil otherwise. A rontolisp namestring is the host spelling, so "absolute" is the leading / -- there is no device or host component to weigh.

Backend support

Works on all four backends (Lisp source, uiop-pathname.lisp).