792d37252f
Created split packages: cur, cur-lib, cur-test, cur-doc, similar to other Racket packages, e.g., redex. * Moved tests out of core and into cur-test * Moved docs into cur-doc * Moved cur implementation and libraries into cur-lib * Added cur meta-pacakge that installs all of the above
58 lines
1.2 KiB
Racket
58 lines
1.2 KiB
Racket
#lang s-exp "../cur.rkt"
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(require "sugar.rkt" "bool.rkt")
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;; TODO: override (all-defined-out) to enable exporting all these
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;; properly.
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(provide Nat z s add1 sub1 plus mult exp square nat-equal? even? odd?)
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(data Nat : Type
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(z : Nat)
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(s : (-> Nat Nat)))
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(define (add1 (n : Nat)) (s n))
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(define (sub1 (n : Nat))
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(match n
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[z z]
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[(s (x : Nat)) x]))
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(define (plus (n1 : Nat) (n2 : Nat))
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(match n1
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[z n2]
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[(s (x : Nat))
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(s (recur x))]))
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(define (mult (m : Nat) (n : Nat))
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(match m
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[z z]
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[(s (x : Nat))
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(plus n (recur x))]))
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(define (exp (m : Nat) (e : Nat))
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(match m
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[z (s z)]
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[(s (x : Nat))
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(mult e (recur x))]))
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(define square (run (exp (s (s z)))))
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;; Credit to this function goes to Max
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(define nat-equal?
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(elim Nat Type (lambda (x : Nat) (-> Nat Bool))
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(elim Nat Type (lambda (x : Nat) Bool)
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true
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(lambda* (x : Nat) (ih-n2 : Bool) false))
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(lambda* (x : Nat) (ih : (-> Nat Bool))
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(elim Nat Type (lambda (x : Nat) Bool)
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false
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(lambda* (x : Nat) (ih-bla : Bool)
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(ih x))))))
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(define (even? (n : Nat))
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(match n
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[z true]
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[(s (n : Nat))
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(not (recur n))]))
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(define (odd? (n : Nat))
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(not (even? n)))
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