Elisp: Check If a Symbol is Defined
Check If Function is Defined
;; check if a function is defined (fboundp 'setq) ; t (fboundp 'xyz) ; nil
Technically,
fboundp check a Symbol's function cell.
Check If Variable is Defined
;; check if a variable is defined (boundp 'tab-width) ;; t (boundp 'xyz) ;; nil
Technically,
boundp checks a Symbol's value cell.
Check Feature
;; check if a feature has been loaded (featurep 'dired)