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From: sherin@linc.cis.upenn.edu (Steve Sherin)
Newsgroups: comp.lang.lisp
Subject: scoops example: stacks
Message-ID: <1229@super.upenn.edu.upenn.edu>
Date: Sun, 24-May-87 01:51:08 EDT
Article-I.D.: super.1229
Posted: Sun May 24 01:51:08 1987
Date-Received: Sun, 24-May-87 08:37:14 EDT
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Reply-To: sherin@linc.cis.upenn.edu.UUCP (Steve Sherin)
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;;; 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)))