;; Arguably FILE-POSITION shouldn't be signalling errors at all; but
;; "NIL if this cannot be determined" in the ANSI spec doesn't seem
;; absolutely unambiguously to prohibit errors when, e.g., STREAM
;; Arguably FILE-POSITION shouldn't be signalling errors at all; but
;; "NIL if this cannot be determined" in the ANSI spec doesn't seem
;; absolutely unambiguously to prohibit errors when, e.g., STREAM