大家好,我需要将我的 F# 代码更改为 Haskell 代码,但我对 Haskell 还很陌生,我不能这样做。我的代码只是从键盘读取数据,如果数据不是整数,则返回错误消息,然后计算 n 斐波那契数,然后写入list 之后将列表写入 txt 文件这是我的代码
open System
let rec fib n =
match n with
|0->0
|1->1
|2->1
|n->fib(n-1)+fib(n-2);;
let printFibonacci list =
for i=0 to (List.length list)-1 do
printf "%d " (list.Item(i));;
let writeToFile list =
let file = System.IO.File.Create("C:\out2.txt")
let mutable s =""
let writer = new System.IO.StreamWriter(file)
try
for i=0 to (List.length list)-1 do
s <- list.Item(i).ToString()
writer.Write(s+" ")
finally
writer.Close()
file.Dispose()
printfn "Writed To File"
let mutable control = true
let mutable num = 0
while control do
try
printfn "Enter a Number:"
num <- Convert.ToInt32(stdin.ReadLine())
let listFibonacci = [for i in 0 .. num-1->fib(i)]
printFibonacci(listFibonacci)
printfn "\n%A"(listFibonacci)
writeToFile(listFibonacci)
control<-false
with
| :? System.FormatException->printfn "Number Format Exception";
Console.ReadKey true|>ignore
fib 0 = 0
fib 1 = 1
fib n = fib (n-1) + fib (n-2)
main = do putStrLn "Enter a number:"
num <- readLn
fibs = map fib [0..n]
mapM' print fibs
然而,由于 haskell 很懒,所以有一种聪明的方法来定义所有斐波那契数的列表。由于您想要该列表的前缀,因此使用此定义更自然(也更有效):
fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
main = do putStrLn "Enter a number:"
num <- readLn
mapM' print (take n fibs)
编辑:写入文件而不是标准输出替换print
with (\num -> appendFile "filename" (show num))
or (appendFile "filename" . show)
.
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