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; A Natural is one of
; - 'Zero
; - (make-next n)
; where n is a Natural
(define-struct next (nat))
; f : Natural -> … ...
(define (f n)
(cond (symbol? n) … (next? n) …(f (next-nat n))…))
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; add-Nat : Natural Natural -> Natural
; Returns the result of adding two Naturals.
(define (add-Nat n m) (cond (symbol? n) m (next? n) (make-next (add-Nat (next-nat n) m))))
Exercises
- Use the stepper on (add-Nat Two Two)to see how it works.
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; A natural is one of
; - 0
; - (add1 n)
; where n is a natural
; f : natural -> … ...
(define (f n) (cond (zero? n) … (positive? n) …(f (sub1 n))…))
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#Factorial, which is defined as
0! = 1, and
(
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n
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+1)! = (
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n
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+1) × (
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n
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!).
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