Created
February 21, 2021 05:34
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何かのタネ
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-- :l Esty | |
module Esty | |
%default total | |
%hide fib | |
%hide fact | |
syntax "sif(" [t] "," [e] ")." [bool] = ifThenElse bool t e | |
namespace Fun | |
-- 階乗、ポイントフリーにはできない | |
partial | |
fact : Nat -> Nat | |
fact x = sif(1, (*x) . fact . (flip minus 1) $ x). (0==) $ x | |
-- フィボナッチ | |
partial | |
fib : Nat -> Nat | |
fib x = sif((sif(0, 1). (0==) $ x), (+ fib . (flip minus 2) $ x) . fib . (flip minus 1) $ x). (1>=) $ x | |
-- コラッツ | |
partial | |
collatz : Nat -> List Nat | |
collatz x = col x [x] where | |
col x ls = sif(ls, sif(col d $ d :: ls, col m $ m :: ls). t). (1==) $ x | |
partial | |
d : Nat | |
d = div x 2 | |
m : Nat | |
m = 3 * x + 1 | |
partial | |
t : Bool | |
t = (0==) $ mod x 2 | |
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