Haskell:预期类型:[Char]实际类型:[[Char]]
我最近开始学习Haskell,在我的程序中,我发现以下错误:Haskell:预期类型:[Char]实际类型:[[Char]],haskell,Haskell,我最近开始学习Haskell,在我的程序中,我发现以下错误: Couldn't match type ‘[Char]’ with ‘Char’ Expected type: [Char] Actual type: [[Char]] In the first argument of ‘head’, namely ‘input’ In the first argument of ‘magi’, namely ‘(head input)’ 我的代码如下所示: vocals = ["a",
Couldn't match type ‘[Char]’ with ‘Char’
Expected type: [Char]
Actual type: [[Char]]
In the first argument of ‘head’, namely ‘input’
In the first argument of ‘magi’, namely ‘(head input)’
我的代码如下所示:
vocals = ["a", "e", "i", "o", "u","y"]
vocal o
| elem o vocals == True = True --return true if the letter is a vowel
| elem o vocals == False = False --else false
magi konsonant = [konsonant] ++ "o" ++ [konsonant]
rovarsprak input
|length input == 0 = ""
|length input > 0 && vocal (head input) == False = magi (head input) ++ rovarsprak (tail input)
|length input > 0 && vocal (head input) == True = head input : rovarsprak (tail input)
据我所知,之所以出现错误,是因为我对head函数的输入是[[char]],而不是[char],但我不明白为什么head的输入是[[char]]。
谢谢 问题在于,
人声
具有以下类型:
vocal :: String -> Bool
或更短:
vocals = "aeiouy"
也就是说,你的代码相当混乱。我们可以将其改写为:
vocals :: [Char]
vocals = "aeiouy"
vocal :: Char -> Bool
vocal = flip elem vocals -- pointfree function
magi :: Char -> String
magi konsonant = konsonant : 'o' : [konsonant]
rovarsprak :: String -> String
rovarsprak "" = "" -- use patterns
rovarsprak (h:t) -- use patterns to unpack
| vocal h = h : rovarsprak t -- == True is not necessary
| otherwise = magi h ++ rovarsprak t -- use otherwise
行vocal=flip elem vocals
的工作原理如下:flip
将函数f
作为输入,该函数包含两个参数x
和y
。然后将其转换为一个函数,该函数接受两个参数y
和x
(因此参数被翻转)
我们想要的是调用
elem o vocals
。这相当于翻转元素人声o
。现在通过使用eta缩减,我们可以省略o
(在子句的头部和正文中)。问题在于vocal
具有类型:
vocal :: String -> Bool
或更短:
vocals = "aeiouy"
也就是说,你的代码相当混乱。我们可以将其改写为:
vocals :: [Char]
vocals = "aeiouy"
vocal :: Char -> Bool
vocal = flip elem vocals -- pointfree function
magi :: Char -> String
magi konsonant = konsonant : 'o' : [konsonant]
rovarsprak :: String -> String
rovarsprak "" = "" -- use patterns
rovarsprak (h:t) -- use patterns to unpack
| vocal h = h : rovarsprak t -- == True is not necessary
| otherwise = magi h ++ rovarsprak t -- use otherwise
行vocal=flip elem vocals
的工作原理如下:flip
将函数f
作为输入,该函数包含两个参数x
和y
。然后将其转换为一个函数,该函数接受两个参数y
和x
(因此参数被翻转)
我们想要的是调用
elem o vocals
。这相当于翻转元素人声o
。现在,通过使用eta缩减,我们可以省略o
(在条款的开头和正文中)。谢谢您的回答!但是我不太清楚这句话是什么意思?谢谢你的回答!但是我不太清楚这行vocal=flip elem vocals
有什么作用?