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module ChurchFold
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open System
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let nil (c:'a->'b->'b) (n:'b) : 'b = n
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let cons (x:'a) (xs:('a->'b->'b)->'b->'b) : ('a->'b->'b)->'b->'b =
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fun c n -> c x (xs c n)
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let toList (xs:('a->'b->'b)->'b->'b) : 'a list =
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xs (fun x acc -> x :: acc) []
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let ofList (ls:'a list) : (('a->'b->'b)->'b->'b) =
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List.foldBack (fun x acc -> cons x acc) ls nil
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let foldWithPredicate (churchList:(int->int list->int list)->int list->int list) (f:int->int->int) (p:int->bool) (acc:int) : int =
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let regularList = toList churchList
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let rec foldTailRec lst accumulator =
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match lst with
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| [] -> accumulator
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| head :: tail ->
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if p head then
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foldTailRec tail (f accumulator head)
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else
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foldTailRec tail accumulator
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foldTailRec regularList acc
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[<EntryPoint>]
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let main _ =
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let numbers = ofList [1; 2; 3; 4; 5]
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let add x y = x + y
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let isEven x = x % 2 = 0
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let greaterThan2 x = x > 2
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printfn "Исходный список: [1; 2; 3; 4; 5]"
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printfn ""
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let sumEven = foldWithPredicate numbers add isEven 0
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printfn "Сумма четных чисел (предикат isEven): %d" sumEven
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let sumGreater2 = foldWithPredicate numbers add greaterThan2 0
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printfn "Сумма чисел больше 2 (предикат > 2): %d" sumGreater2
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let multiply x y = x * y
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let productEven = foldWithPredicate numbers multiply isEven 1
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printfn "Произведение четных чисел: %d" productEven
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printfn ""
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printfn "Демонстрация работы с различными предикатами:"
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let isOdd x = x % 2 = 1
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let sumOdd = foldWithPredicate numbers add isOdd 0
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printfn "Сумма нечетных чисел: %d" sumOdd
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let isPositive x = x > 0
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let countPositive = foldWithPredicate numbers (fun acc _ -> acc + 1) isPositive 0
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printfn "Количество положительных чисел: %d" countPositive
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0 |
