9 lines
308 B
Racket
9 lines
308 B
Racket
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(struct stack ([items #:auto]) #:mutable #:auto-value '())
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(define (push! x stack)
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(set-stack-items! stack (cons x (stack-items stack))))
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(define (pop! stack)
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(begin0 (car (stack-items stack))
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(set-stack-items! stack (cdr (stack-items stack)))))
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(define (empty? stack)
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(null? (stack-items stack)))
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