17 lines
453 B
Racket
17 lines
453 B
Racket
#lang sicp
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(define (attach-tag type-tag contents)
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(cond ((number? contents) contents)
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(else (cons type-tag contents))))
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(define (type-tag datum)
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(cond ((number? datum) 'scheme-number)
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((pair? datum) (car datum))
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(else (error "Bad tagged datum -- TYPE-TAG" datum))))
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(define (contents datum)
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(cond ((number? datum) datum)
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((pair? datum) (cdr datum))
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(else (error "Bad tagged datum -- CONTENTS" datum))))
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