8 lines
475 B
Forth
8 lines
475 B
Forth
// Y combinator with injected laziness. GordonBGood : April 18, 2025
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type 'T Mu = { eval: 'T Mu -> 'T }
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let Y f = let g = fun x -> f <| fun() -> (x.eval x) in g { eval = g }
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let fibonacci n = Y (fun fn f s i -> if i >= n then f else fn () s (f + s) (i + 1)) 1I 1I 1
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let factorial n = Y (fun f p x -> if x > n then p else f () (x * p) (x + 1I)) 1I 1I
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printfn "fibonacci 10 = %A\r\nfactorial 5 = %A" (fibonacci 10) (factorial 5I)
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printfn "fibonacci 1000 = %A" (fibonacci 1000)
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