egison-3.7.0: lib/math/geometry/differential-form.egi

;(define $d
;  (lambda [%X]
;    !(∂ X)))

(define $wedge
  (lambda [%X %Y]
    !(. X Y)))

(define $Lie.wedge
  (lambda [%X %Y]
    (- !(. X Y) !(. Y X))))

;(define $hodge
;  (lambda [%A]
;    (* (sqrt (abs (det g_#_#)))
;       (foldl . ε_i.1..._i.n A_j.1..._j.k
;              (map (lambda [$l] g~i.l~j.l) (between 1 k))))
;    ))