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@ -25,9 +25,20 @@ |
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(define (prepend first-value) (lambda (rest) (cons first-value rest))) |
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;=============== combinators ====================== |
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(define (Y f) (f (lambda (x) ((Y f) x)))) |
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(define (Y2 f) (f (lambda (x y) ((Y2 f) x y)))) |
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(assert-eq "Y test 1 (factorial) failed" |
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120 |
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((Y (lambda (f) (lambda (n) (if (= n 0) 1 (* n (f (- n 1))))))) 5)) |
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(assert-eq "Y2 test 1 (pascal triangle) failed" |
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35 |
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((Y2 (lambda (f) (lambda (a b) |
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(if (= a 0) 1 (if (= b 0) 1 (+ (f (- a 1) b) (f a (- b 1)))))))) |
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3 4)) |
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(define (reduce-right initial reducer) (Y |
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(lambda (f) (lambda (values) |
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(if (null? values) initial (reducer (car values) (f (cdr values)))))))) |
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