目前,我正在努力学习折叠。
但不是采用预定的功能我想用我自己的。
所以我希望双所有元音在一串。
doubleVowels :: String -> String
我尝试(但只是'a',因为我是试图解决这个问题对一个字母的第一个,并将扩大和优化它,一旦运行):
doubleVowels :: String -> String
doubleVowels a = foldl (\eachChar -> if eachChar == 'a' then (a ++ "aa") else a) "" a
试图运行他的代码我让下述错误:
Experimenting.hs:8:78: error:
* Couldn't match type `[Char]' with `Char -> Char'
Expected type: Char -> Char
Actual type: String
* In the expression: a
In the expression: if eachChar == 'a' then (a ++ "aa") else a
In the first argument of `foldl', namely
`(\ eachChar -> if eachChar == 'a' then (a ++ "aa") else a)'
|
8 | doubleVowels a = foldl (\eachChar -> if eachChar == 'a' then (a ++ "aa") else a) "" a
| ^
Experimenting.hs:8:81: error:
* Couldn't match expected type `Char' with actual type `[Char]'
* In the second argument of `foldl', namely `""'
In the expression:
foldl
(\ eachChar -> if eachChar == 'a' then (a ++ "aa") else a) "" a
In an equation for `doubleVowels':
doubleVowels
= foldl
(\ eachChar -> if eachChar == 'a' then (a ++ "aa") else a) "" a
|
8 | doubleVowels a = foldl (\eachChar -> if eachChar == 'a' then (a ++ "aa") else a) "" a
| ^^
Failed, no modules loaded.