gistfile1.txt

;; given a store loc l and two stores S_1 and S_2, return the lub of
;; S_1(l) and S_2(l).  We know that every l this function gets is
;; going to be in the domain of either S_1 or S_2 or both.
(define-metafunction lambdapar
  lubstore-helper : S S l -> D
  [(lubstore-helper S_1 S_2 l)
   ,(let ([d_1 (term (store-lookup S_1 l))]
          [d_2 (term (store-lookup S_2 l))])
      (cond
        [(equal? d_1 (term lookupfailed)) d_2]
        [(equal? d_2 (term lookupfailed)) d_1]
        [else (term (lub ,d_1 ,d_2))]))])