sherin@linc.cis.upenn.edu (Steve Sherin) (05/24/87)
;;; Stacks with Scoops--Steve Sherin (define-class stack (instvars the-stack) (options inittable-variables gettable-variables settable-variables)) (define-method (stack push) (value) (set! the-stack (cons value the-stack))) (define-method (stack tos) () (if the-stack (car the-stack))) (define-method (stack pop) () (if the-stack (let ((top (tos))) (set! the-stack (cdr the-stack)) top)))