featurep

Arguments: feature-or-list-of-features

This function returns true if the argument correctly describes the state of the *features* list and nil if it does not. feature-or-list-of-features can be any atom or list acceptable to the reader macros #+ and #- (and so can include not, and and or and can contain sublists). Note that the :version>= extension used by Allegro CL is often useful (see Reader macros and cl:*features* in implementation.htm). The Allegro CL style is for features to be keywords. If the argument is an atom, the subsequence of *features* starting at that feature is returned if it is present and nil if it is not.

Examples:

(excl:featurep :gsgc) -> (:gsgc :clos ...)
(excl:featurep :foo) -> nil
(excl:featurep '(and (or :unix :foo))) -> t

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Created 2019.8.20.